Spread spectrum transceiver module utilizing multiple mode transmission

ABSTRACT

A data transceiver module for digital data communications in a portable hand-held data terminal has multiple data spread spectrum modes which include direct sequence and frequency function modulation algorithms. The transceiver module has multiple user or program configurable data rates, modulation, channelization and process gain in order to maximize the performance of radio data transmissions and to maximize interference immunity. Various module housings, which may be PCMCIA type, are able to be mated with a suitably designed data terminal. Media access control protocols and interfaces of multiple nominal operational frequencies are utilized. Wireless access devices in a cell based network each consider a variety of factors when choosing one of a plurality of modes of wireless operation and associated operating parameters. Such selection defines a communication channel to support wireless data, message and communication exchanges. In further embodiments, the wireless access devices also support a second channel, a busy/control channel, for managing communication on the main communication channel and to overcome roaming and hidden terminal problems. Roaming terminal devices are also configured to support the dual channel design. Such configuration in both circumstances may involve the use of a multimode radio that is timeshared between the two channels or two radios, one dedicated to each channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/US96/09474 filed Jun. 3, 1996, which claims priority from U.S.application Ser. No. 08/645,348 filed May 13, 1996, U.S. applicationSer. No. 08/544,815 filed Oct. 18, 1995, U.S. application Ser. No.08/513,658 filed Aug. 11, 1995, and U.S. application Ser. No. 08/457,697filed Jun. 1, 1995 all of them are abandoned.

BACKGROUND

1. Technical Field

The present invention relates generally to communication networksutilizing spread spectrum radio transceivers, and, more specifically, tomulti-hop RF networks wherein participating devices utilize spreadspectrum transceivers that are capable of operating in any of a varietyof spread spectrum modes. The spread spectrum modes include, forexample, direct sequence transmission across a spreading bandwidth orchannelized across the spreading bandwidth, frequency hoppingtransmission across all or a part of the spreading bandwidth, a hybridcombination of direct sequence transmissions and frequency hoppingtransmissions, and transmissions on a portion of the spreadingbandwidth. The selection of a spread spectrum mode of operation dependsupon signal conditions and characteristics of members capable ofcommunication within the RF communication network.

2. Description of Related Art

Communication devices within a wireless local area network employwireless communication links to transfer data and commands within thelocal area network. Typical units within a wireless local area networkinclude stationary wireless access devices, mobile radio units, mobileimage capture units, printing units, and other units operative with thedata and commands. These units often link to a wired local area networkthrough a wireless access device to transfer data and commands todevices located on the wired network. The wireless local area networkstypically employ cellular communication techniques to provide thewireless communication links within the local are network.

One common installation of a wireless local area network serves factoryautomation functions. Because hard-wiring a local area network within alarge, dynamic facility is both expensive and difficult, the wirelesslocal are network provides traditional network functions as well asadditional functions germane to the wireless attributes of the network.However, due to difficult transmission and interference conditionswithin a factory, establishing and maintaining sufficient wirelesscommunication ties oftentimes proves difficult. Attenuation oftransmitted signals, multi-path fading, ambient noise, and interferenceby adjacent cells often disrupts communication within the wireless localarea network.

Spread spectrum transmissions are often used in attempts to overcomecommunication problems. With spread spectrum transmissions, thebandwidth over which information is broadcast is deliberately made widerelative to the information bandwidth of the source information. Spreadspectrum transmission techniques include direct sequence transmission,frequency hopping transmission, a combination of direct sequencetransmission and frequency hopping transmission, and may include othertechniques that deliberately transmit over a wide spectrum.

Direct sequence spread spectrum transmitters typically spread by firstmodulating a data signal with a pseudo random chipping sequence at amultiple of the source data clocking rate. Once constructed, thecomposite modulation is coupled to a carrier via modulation techniquesand then transmitted. Phase modulation is typically employed, butfrequency modulation or other types of modulation may also be used.Circuitry in a receiving units receives the signal, decodes the signalat the multiple of the source data clocking rate using a particularchipping sequence, and produces received data. In a typical directsequence system, the pseudo random chipping sequence applied by thereceiving unit corresponds to all, or respective portions, of thetransmitted signal. In this fashion, the receiving unit receives onlyintended data and avoids receiving data from adjacent cells operating onthe same frequency. Direct sequence spread spectrum modes also providesignificant noise rejection characteristics since each component of thesource data is essentially transmitted multiple times. The receivedsignal is therefore a composite that may be averaged or weighted toavoid receiving improper data or falsing based upon noise.

A frequency hopping system commonly uses conventional narrowbandmodulation but varies the modulation frequency over time in accordancewith a known pattern or algorithm, effectively moving the modulatedsignal over the intended spreading bandwidth. The spread spectrum signalis only discernible to a receiver that has prior knowledge of thespreading function employed and which has obtained synchronization withthe spreading operation at the transmitter. By spreading transmissionsover the spreading bandwidth, particular portions of the spreadingbandwidth within which transmission is difficult may be substantiallyavoided.

In the United States and many other countries, spread spectrumcommunications is used commercially within designated Industrial,Scientific and Medical (ISM) bands. These bands are structured asmulti-use bands containing non-communications equipment such asindustrial and commercial microwave ovens as well as low power consumergrade transmitters, vehicle location and telemetry systems and otherspread spectrum devices of differing characteristics. Operation in ISMbands is unlicensed and uncoordinated, so equipment operating in thesebands must be designed to operate successfully without knowledge of thetypes of devices that may be used in close proximity. The spreadspectrum system design must also take into consideration the occupantsof the spectrum adjacent to the ISM bands which may be both potentialsources of interference to, and susceptible to interference from,various types of spread spectrum products.

Various forms of modulation across the spreading band may be utilized incommercial spread spectrum packet data communication systems. Full banddirect sequence systems occupy the entire width of an ISM band. Thespreading ratio, the ratio of the bandwidth of the spread spectrummodulated signal to the information bandwidth of the source modulation,determines the process gain of the system. Regulations within the UnitedStates mandate a minimum process gain of 10 dB, which is determined fromten times the logarithm of the spreading ratio. Process gain is ameasure of the ability of a spread spectrum system to resistinterference. The larger the spreading ratio, the more resistant thesystem is to interference within the receiver bandwidth. Wide bandwidthmodulation is reasonably resistant to low or moderate levels ofinterference, but even systems with relatively high process gainsexperience difficulties when subject to strong interference.

When system throughout requirements dictate high data rates, the minimumprocess gain requirements in the regulations necessitate using widebandwidth transmissions. For example, a well-known system NCR Wavelanuses Quadrature PSK modulation at 1 million symbols per second toachieve 2 megabits per second (MBPS) data rates with a sourceinformation bandwidth available in the US ISM band at 902 MHz band. Inpractice, implementation constraints dictate that this system uses thefull 26 MHz band. Systems operating at other data rates, including theoriginal Norand system, utilize the full bandwidth at lower source datarates, e.g., 200 kilobits per second (KBPS). Utilization of a widerspreading bandwidth in this case provides greater rejection of multipathfading typical of the indoor RF signal propagation environment.

When it is anticipated the direct sequence systems may be used inenvironments with strong in-band interference, a design choice is toemploy channelization to reject interference. In the case of channelizeddirect sequence (DS) modulation, the spreading bandwidth is reduced to afraction of the total available bandwidth, and a frequency-agilefrequency generation systems is employed. By selecting the carrierfrequency of operation, communications can be established in a portionof the band where interference is not present. This technique requiresthe use of selective filters in the receiver intermediate frequency (IF)section to provide the necessary interference rejection. Thesechannelized DS systems utilize interference avoidance rather thanrelying on process gain to reject interference.

Utilization of frequency hopping spread spectrum systems is appropriatein environments where interference within the band of operation is notconfined to particular portions of the band, but may periodically arisein various parts of the entire band. Frequently hopping is also usefulas a multiple access technique. Use of multiple hopping sequencesconcurrently within a given location allows many simultaneouscommunication sessions to be supported. Occasionally, devices operatingon different hopping sequences will simultaneously occupy the samechannel within the band for short periods of time. For moderate numbersof simultaneous hopping sequences, this occurs infrequently.

Frequency hopping also provides similar multipath rejection capabilitiesto wideband direct sequence modulation. If a particular channel ofoperation is in a fade temporarily preventing communication, a jump to afrequency sufficiently removed from the faded frequency will often allowcommunications to resume.

Frequency hopping systems require more protocol overhead to aid inestablishing and maintaining synchronization between units sharing agiven hopping sequence. Additionally, the initial acquisition of thehopping sequence may require that an unsynchronized device scan the bandfor a period equivalent to may hop times. The overhead for directsequence systems is lower, with several bit-times usually allocated toreceiver acquisition at the beginning of each transmission.

Spread spectrum communications may not be appropriate for someapplications. For example, short hop communications such ascommunications between a portable hand-held terminal and a peripheraldevice such as a scanner or printer over a short distance is a very costsensitive application. Spread spectrum operation requires more circuitcomplexity and power consumption than is tolerable for this application.Simpler FM or AM techniques such as ON-OFF-Keying (OOK) may bedesirable.

Conventionally, the particular spread spectrum modulation technique ischosen according to the particular applications in which the datatransceiver is to be utilized. For example, in a small warehouse havingfew RF barriers, minimal interference from cellular and wireless phones,and minimal amounts of communication traffic, radio transceivers usedtherein might only employ direct sequence spread spectrum transmissiontechniques. Thus, conventionally, such transceivers would bespecifically designed, constructed and installed. However, afterinstallation, if communication traffic or local noise increases, thecommunication might fail to function as required. Likewise, afterinstallation, if RF barriers are installed or if the network is moved toan urban environment with a great deal of noise from neighboringinstallations, cellular and mobile phones, etc., the network may fail tomeet the needs of the customer.

Similarly, a design might be based on a customer's needs for a smallstore in a downtown urban area. Because of the greater likelihood of agreat amount of radio frequency traffic in the vicinity, the customerrequires a radio which is free from interference from nearby radiotransmissions with little concern for operating range. Consequently, adifferent specific type of radio would be designed to meet the needs ofthe corporation based upon the operating conditions in which the radiois to be used, for example using frequency hopping modulation.

In the exemplary installations mentioned above, each of the radios wouldbe optimized to meet the needs of the customer. However, a customer'sneeds continually change, and, if the particular application orenvironment were to change justifying a different spread spectrummodulation technique, the customer is either forced to change all oftheir radio transceivers or live with the under-performance theycurrently receive.

Moreover, in a typical network installation, a client may have diverseoperational requirements. For example, the particular applications ofthe radio unit may change several times within the same day. The sitemay also have areas which are relatively noise and barrier free andthose which encounter heavy noise and barriers. Some areas may have hightraffic volume, while others experience only occasional traffic. In suchnetworks, a single radio transceiver design can never provide optimalperformance in all areas. Sacrifices are made in the designcharacteristics of the transceivers in an attempt to provide bestperformance overall.

Similarly, in mobile contexts, a worker may require mobilecommunications to a vehicle based information system or forwarding to acentral communication facility through a vehicle based radio WANtransceiver. The characteristics of the communications medium for thisclass of operation vary greatly. Interference will vary from location tolocation. Additionally, it is necessary to allow operation if the workermoves away from the vehicle or inside a building structure. Because eachwireless local area network may have been designed for a particular setof criteria with particular spread spectrum operational abilities,mobile units may be non-functional within particular wireless local areanetworks.

Thus, there is a need in the art for a communication network thatoperates dynamically to optimize communication utilizing various spreadspectrum transmission techniques, considering the characteristics of RFnoise, neighboring interference, RF barriers, participating transceiverunit capabilities and applications to be performed in such dynamicoptimization.

It is another object of the present invention to provide a spreadspectrum RF transceiver module, for use in wireless network devices,which utilizes multiple spread spectrum modulation techniques providingmultiple configurable modes of data transmission, whereby modes may beselected to attain optimal transmission performance.

A further object of the present invention is to provide an RF datatransceiver module which combines frequency hopping and direct sequencetransmission techniques within a single design.

It is an object of the present invention to provide a spread spectrum RFtransceiver module which utilizes common media access protocols andinterfaces for multiple nominal carrier frequencies and modulationparameters.

It is a further object of the present invention to provide a spreadspectrum RF transceiver utilizing 900 MHz transmission and having astandard interface with common 2.4 GHz transmission.

It is a further object of the invention to provide a spread spectrum RFtransceiver which may be utilized in several different types ofmulti-layered data communications networks.

Another object of the present invention is to produce a wireless localarea network and packet wireless data communication system that isflexible to operate reliably in varied and unpredictable RF propagationand interference environments.

A further object of the present invention is to provide a wireless RFtransceiver module capable of utilizing a variety of operational modesthereby allowing large business operation to purchase a single productmeeting a multiple usage needs maximizing operational flexibility andminimizing sparing and service concerns.

It is another object of the present invention to provide a modularwireless LAN modem capable of supporting multiple modes of operationunder a single media access protocol with a standardized interface to ahand-held portable data terminal such that the wireless LAN modem maydynamically change modes of operation transparently to the host device,not requiring that the host device be aware of changes in the modes ofoperation, or that operation of higher protocol layers be impacted.

Yet another object of the present invention is to produce a modularwireless LAN modem that may be utilized for both in-premise and workerto vehicle application, and for short range communications to peripheraldevices.

These and other objects of the invention will be apparent fromexamination of the drawings and remainder of the specification whichfollows.

SUMMARY OF THE INVENTION

The system and radio of the present invention to overcome thelimitations of the prior devices as well as other limitations thereforemay operate in any of a plurality of spread spectrum modes. A selectedspread spectrum mode, or set of spread spectrum modes, is based uponsystem characteristics as well as transmission characteristics within anoperating environment.

One particular operating environment relates to multi-hop wirelessnetworks that are subject to in-band interference and multi-path fading.However, in these systems, members (hereinafter “transceiver devices”)of the network may have different operating capabilities. Therefore, thesystem and radio of the present invention provide a mechanism forselecting spread spectrum modes of operation to satisfy network memberlimitations, data transmission throughput requirements, neighboringsystem non-interference requirements, as well as noise tolerancerequirements.

By providing a dynamic mechanism for selecting spread spectrum modes ofoperation, the present invention provides many import objects andadvantages that will become apparent with reference to the entirespecification and drawings. In particular, in one embodiment, acommunication network for collecting and communicating data isdisclosed. The network comprises a wireless access device and at leastone mobile terminal. The wireless access device comprises a controlcircuit and a first RF transceiver that selectively operates in one of aplurality of spread spectrum modes. The at least one mobile terminalcomprises a second RF transceiver that operates in at least one of aplurality of spread spectrum modes. The control circuit responds totransmissions received from the first RF transceiver to evaluatecommunication performance and dynamically selects one of the pluralityof spread spectrum modes of the first RF transceiver. Such selectionalso takes into consideration the at least one of the plurality ofspread spectrum modes of the second RF transceiver.

Further, the plurality of spread spectrum modes of the first RFtransceiver may comprise direct sequence transmission, frequencyhopping, channelized direct sequence and/or hybrid frequency hopping(direct sequence) modes. The control circuitry may evaluatecommunication performance through reference to received signal strengthindications, transmission success rate and neighboring cell operatingcharacteristics.

Other aspects may be found in a communication system for collecting andcommunicating data using wireless data signal transmission. Therein awireless access device capable of communicating with a plurality ofradios comprises a radio capable of operating in a plurality of spreadspectrum modes. The wireless access device also comprises a spreadspectrum mode controller responsive to transmissions and data receivedfor evaluating the data communication system and for controlling theradio to selectively operate in a spread spectrum mode among a pluralityof spread spectrum modes.

The wireless access device may further comprise circuitry for evaluatingthe plurality of spread spectrum modes to select a spread spectrum modeof operation. Such selection may take involve the identification of acommon spread spectrum mode.

Yet other aspects can be found in a data communication system havingspread spectrum capability for collecting and communicating data usingwireless data signal transmission. Therein, an RF transceiver comprisesan modulator having a spreader, a demodulator having a despreader, acontrollable oscillator attached to the modulator and demodulator, andcontrol circuitry that both selectively enables the spreader anddespreader and selectively controls the controllable oscillator to causeoperation in one of a plurality of modes of spread spectrum operation.

The data communication system may further comprising a host controllerthat directs the control circuitry in the selection of the one of theplurality of modes of spread spectrum operation. The host controller maycomprise wireless access device control circuitry. In addition, thecontrol circuitry may wirelessly receive instruction regarding selectionof the one of the plurality of modes of spread spectrum operation. Manyother aspects of the present invention will be appreciated with fullreference to the specification, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a wireless communication network builtin accordance with the present invention which incorporates dynamicallyadapting spread spectrum transceivers and supporting communicationprotocols;

FIG. 1B is a flow diagram illustrating the operation of a wirelessaccess device in accordance with present invention whereby multiplewireless devices having potentially different transceiver capabilitiesare supported;

FIG. 1C is a block diagram illustrating a radio transceiver built inaccordance with the present invention to provide multiple modes ofoperation;

FIG. 1D is a block diagram illustrating the operation of the wirelessaccess device having the multi-mode transceiver of FIG. 1C installedtherein.

FIG. 2A is a front elevation view of one embodiment of a hand-heldportable data terminal having a transceiver module built in accordancewith the present invention;

FIG. 2B is a side elevation view of the hand-held portable data terminalof FIG. 2A showing a module of the present invention;

FIG. 3 is a side evaluation view of the hand-held portable data terminalof FIG. 2A showing a module of the present invention;

FIG. 4 is a side elevation view of the hand-held portable data terminalof FIG. 2A showing a removably insertible module of the presentinvention;

FIGS. 4A, 4B and 4C illustrate in detail the cooperation between a radiomodule and the hand-held portable data terminal shown in FIG. 3.

FIG. 5 is a perspective view of another hand-held portable data terminalwhich may incorporate the present invention;

FIG. 6 is a side elevation view of the data terminal of FIG. 5 showingan extendibly retractable rotating carriage housing for receiving amodule incorporating the present invention;

FIG. 7 is an exploded view of a radio module incorporating the presentinvention;

FIG. 8 is an exploded view of a radio module of the present inventionfurther containing a scanner;

FIG. 9 is an exploded view of a radio module of the present inventioncontained within a PCMCIA type housing;

FIG. 10 is a functional block diagram of the architecture of the radiomodules of the present invention;

FIG. 11 is a conceptual block diagram of the operation of thetransmitter of FIG. 10 when operating in a direct sequence spreadspectrum transmission mode;

FIG. 12 shows a conceptual diagram of the operation of the receiverutilized in conjunction with the transmitter of FIG. 11;

FIG. 13 is a block diagram of an embodiment of a receiver of the presentinvention;

FIG. 14A is a diagram of the pseudo-random number generator shown inFIG. 10;

FIG. 14B is a schematic block diagram illustrating the interaction ofthe pseudo-random number generator of FIG. 14A with traverse filteringand formatter circuitry of FIG. 10;

FIG. 15 is a block diagram illustrating the frequency generatorcircuitry as shown in FIG. 10;

FIG. 16 is a block diagram illustrating the transmitter circuitry asshown in FIG. 10;

FIG. 17 illustrates the circuitry for selecting between the modes ofmodulation of the present invention.

FIG. 18 is a block diagram of the MAC circuitry as shown in FIG. 10;

FIG. 19 is a block diagram illustrating the host interface circuitry asshown in FIG. 10 for the radio module of FIG. 7 and for theradio/scanner module of FIG. 8; and

FIG. 20 is a block diagram illustrating the host interface circuitry asshown in FIG. 10 for the radio module of FIG. 9.

FIG. 21 is a diagram illustrating an alternate configuration of portabledata terminals according to the present invention.

FIG. 22A illustrates one embodiment of the data collection terminal ofthe present invention, having both wired and wireless communicationcapability.

FIG. 22B is a diagram illustrating a specific implementation of theportable terminal of FIG. 22A a single PCMCIA card contains not only amulti-mode wireless transceiver, but also a wired modem transceiver.

FIG. 23 is a diagram illustrating the use of portable terminalsaccording to the present invention utilizing both wired and wirelesscommunication in a network configuration.

FIG. 24 is a diagram illustrating the use of portable data terminalsaccording to the present invention utilizing both wired and wirelesscommunication to access separate subnetworks in an overall communicationnetwork.

FIG. 25a is a block diagram illustrating an embodiment of the presentinvention wherein a wireless access device uses a dedicated control/busychannel to manage a plurality of modes of communication with roamingterminals.

FIG. 25b is a drawing illustrating advantageous operation of thewireless access device of FIG. 25a when two roaming terminals encounterhidden terminal conditions.

FIG. 25c is a flow diagram illustrating the functionality of thewireless access device of FIGS. 25a-b in managing communication using acontrol/busy channel.

FIG. 26a is a block diagram illustrating an alternate embodiment of thatshown in FIG. 25a wherein a wireless access device uses a separatetransmitter for the dedicated control/busy channel and a roamingterminal uses either a shared multimode transmitter or a multimodetransmitter and a separate busy/control channel receiver.

FIG. 26b is a drawing illustrating advantageous operation of thewireless access device of FIG. 26a when the two roaming terminalsencounter hidden terminal conditions.

FIG. 26c is a flow diagram illustrating the functionality of thewireless access device of FIGS. 26a-b in managing communication using acontrol/busy channel.

FIG. 27 is a block diagram illustrating a further embodiment of thepresent invention wherein channel selection and operating parameters aredelivered by a wireless access device on a dedicated busy/controlchannel with or without multimode transceiver capabilities.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A illustrates a communication network 1 incorporating theteachings of the present invention. The system comprises wireless accessdevices 2A, 2B and 2C, portable transceiver units 4A, 4B and 4C, awireless code reader 5 and a peripheral device 6. The wireless accessdevices 2A and 2B communicate directly on a wired network 3 to eachother and to other wired network devices (not shown). The wirelessaccess device 2C communicates with the wired network 3 and the wirelessaccess device 2A via wireless transmissions through the wireless accessdevice 2B.

The wireless access 2A-C may comprise wireless access points or wirelessaccess servers to provide an interface among the portable transceiverunits 4A-C, the code reader 5, the peripheral device 6 and devices onthe wired network. Each of these wireless access devices 2A-C hasassociated with it a range or cell of communication. For example, theportable transceiver units 4A-C may wander in and out of range of thewireless access device 2A. Similarly, they may wander in and out ofrange of the wireless access devices 2B-C, i.e., they may wander fromcell to cell. Each access device 2A-C, and many more as may provenecessary, are located to provide coverage of a customer's premises.Cell areas typically overlap somewhat to support ubiquitous coverage.

Because cells typically overlap slightly with one another, at any time,a hand-held radio unit may communicate with at least two wireless accessdevices. To avoid conflicts with transmissions in such overlap areas, itis desirable to configure neighboring cells operate with differentspreading codes, different hopping sequences or different modes, forexample. However, when the portable transceiver unit 4B for examplepasses from one cell to another, it cannot communicate with aneighboring wireless access device without changing its operatingcharacteristics. Thus, the present invention provides several techniquesfor accommodating devices wishing to communicate in a new cell.

Moreover, the wireless access devices 2A-C, peripheral device 6 and codereader 5 may be capable of only some modes of wireless operation. Thus,the present invention provides a mechanism for each of the wirelessaccess devices 2A-C to dynamically attempt to select a common mode ofappropriation for each participating device within its cell. Moreover,if a given mode of operation proves dissatisfactory, a wireless accessdevice may dynamically switch modes to attempt to achieve superiorperformance.

In particular, data throughput concerns and requirements, ambient noise,power consumption of portable units, previously recorded success rates,received signal strength indications, neighboring cell operating modesand success rates, and mode capabilities of participating devices areall considered in determining the mode in which to operate. Eachwireless access device engages in such consideration when initiallyestablishing communication in its cell, when attaching or detaching aparticipating device and as channel conditions are evaluated. In otherembodiments, less than all of such considerations need be made. Forexample, where all transceivers are known to operate in all availablemodes, consideration of this factor is not necessary. Similarly, if onlyone cell exists or if problems in overlap regions prove minimal,consideration of neighboring cell operation need not be engaged.Likewise, received signal strength alone may be used as a modeperformance indication.

Using lower power transmissions, a benefit to battery powered portabletransceiver units, requires the use of more wireless access devices tocover a premises. Lower power transmissions might also or alternatelyrequire a mode having a wider spreading bandwidth or slower datatransfer rate to overcome the lower received signal strength. In othercells that have minimal battery power concerns and little or no noise, aspread spectrum mode may be chosen that provides higher datatransmission rates. In yet other cells experiencing significantbackground noise, a direct sequence spreading mode may be employed thatprovides greater noise tolerance.

In addition to changing modes, the wireless access devices 2A-C alsosupport changes to various mode parameters such as data segment sizes,chipping rates, spreading code lengths, etc. By supporting dynamicchanges in operating modes and mode parameters, the communicationnetwork 1 attempts to accommodate any transceiving device that entersany cell. This flexibility allows for expansion without replacingexisting equipment. An older radio transceiver may be able toparticipate with newer transceivers that may support newer modes ofoperation. The network 1 would attempt to accommodate such communicationin a common, older mode of operation.

RF signals are inherently subject to what is termed “multipath fading”.A signal received by a receiver is a composite of all signals that havereached that receiver by taking all available paths from thetransmitter. The received signal is therefore often referred to as a“composite signal” which has a power envelope equal to the vector sum ofthe individual components of the multipath signals received. If thesignals making up the composite signal are of amplitudes that add “outof phase” the desired data signal decreases in amplitude. If the signalamplitudes are approximately equal, an effective null (no detectablesignal at the receiver) results. This condition is termed “fading”.

Normally changes in the propagation environment occur relatively slowly,i.e., over periods of time ranging from several tenths ({fraction(1/10)}'s) of seconds to several seconds. However, in a mobile RFenvironment, receivers (or the corresponding transmitters) of ten travelover some distance in the course of receiving a message. Because thesignal energy at each receiver is determined by the paths that thesignal components take to reach that receiver, the relative motionbetween the receiver and the transmitter causes the receiver toexperience rapid fluctuations in signal energy. Such rapid fluctuationscan result in the loss of data if the amplitude of the received signalfalls below the sensitivity of the receiver.

Over small distances, the signal components that determine the compositesignal are well correlated, i.e., there is a small probability that asignificant change in the signal power envelope will occur over thedistance. If a transmission of a data packet can be initiated andcompleted before the relative movement between the receiver andtransmitter exceeds the “small distance” data loss to fading is unlikelyto occur. The maximum “small distance” wherein a high degree ofcorrelation exists is referred to hereafter as the “correlationdistance”.

As expressed in wavelengths of the carrier frequency, the correlationdistance is on half (½) of the wavelength, while a more conservativevalue is one quarter (¼) of the wavelength. Taking this correlationdistance into consideration, the size of the data packet forsegmentation purposes can be calculated. For example, at 915 MHz (apreferred RF transmission frequency), a quarter wavelength is about 8.2centimeters. A mobile radio moving a ten (10) miles per hour, or 447centimeters per second, travels the quarter wavelength in about 18.3milliseconds. In such an environment, as long as the segment packet sizeremains well under 18.3 milliseconds, significant signal fluctuationsduring the duration of a packet transmission is unlikely. In such anpreferred embodiment, five (5) millisecond data packet segments arechosen which provides a quasi-static multipath communicationenvironment.

The faster the relative movement between a transmitter and a receiverthe greater the effect of fading. Similarly, if the relative movement isslower, fading is less pronounced. In many communication environments,the degree of fading effects varies dramatically both from time to timeand from installation to installation.

One example of a receiver making such a measurement of fading can befound in the abandoned patent application of Ronald L. Mahany. U.S. Ser.No. 07/485,313, filed Feb. 26, 1990, which is incorporated herein byreference. Specifically, in that reference, a received signal strengthindicator (RSSI) circuit is found in the receiver. The RSSI circuitsample the signal strength of a transmission. If the signal strengthsamples are evaluated in sequence and the trend analyzed, the degree offading can be measured. If the signal strength samples decrease invalue, it is likely that fading is present in the network.

A transceiver using direct-sequence spread spectrum transmission uses aspreading-code of a higher frequency than that of the data rate toencode the data to be sent. This higher frequency is achieved byincreasing the chip clock rate (wherein each chip constitutes an elementof the spreading-code). Using the same spreading code, the receiverdecodes the received signal while ignoring minor faults which occurredin transmission, providing noise immunity and multi-path signalrejection. The frequency and length of the spreading-code can be variedto offer more or less multi-path signal rejection or noise immunity.Although it may result in improved communication, increasing thefrequency or length of the spreading-code requires additional overheadwhich may not be justifiable unless necessary.

Frequency-hopping is the switching of transmission frequencies accordingto a sequence that is fixed or pseudo-random and that is available toboth the transmitter and receiver. Adaptation to the communicationenvironment via an exchange in frequency-hopping operating parameters ispossible, for example, via selective control of the hopping rate orthrough the use of coding or interleaving. The greater the degree offrequency selectivity of the fading envelope (i.e., when fading issignificant only over a portion of the spectrum of hopping frequencies),the greater the benefit of such adaptation.

Particularly, a parameter indicating the hopping rate can be varied tominimize the probability that the channel characteristics willdetrimentally change during the course of a communication exchange. Tovary the hopping rate is to vary the length of a hopping frame. Althoughmultiple data (or message) exchanges per hopping frame is contemplated,the preferred hopping frame consists of a single exchange of data, Forexample, in a polling environment, the hopping frame might consistof: 1) a base station transmitting a polling packet to a roamingterminal; 2) the roaming terminal transmitting data in response; and 3)the base station responding in turn by transmitting an acknowledgepacket. Each hopping frame exchange occurs at a differentpseudo-randomly chosen frequency.

For optimization, the hop frame length is adjusted to be as long aspossible, while remaining shorter than the coherence time of the channelby some safety margin. Although such adjustment does not eliminate theeffects of fading, it increases the probability that the characteristicsof the channel will remain consistent during each hopping frame. Thus,in the preferred embodiment, if the polling packet transmission issuccessfully received, the probability of successful receipt of the data(or message) and acknowledge is high.

Another parameter for changing frequency-hopping performance is that ofcoding. Coding on the channel for error correction purposes can beselectively used whenever the probability of data or message loss due tofading is high. In particular, coding methods which provide burst errorcorrection, e.g., Reed-Solomon coding, can be applied if the hop lengthis likely to exceed the coherence time of the channel. Such codingmethods allow some portion of the data to be lost and reconstructed atthe expense of a 30-50% reduction in throughput. The operating parameterfor coding indicates whether coding should be used and, if so, the typeof coding to be used.

An operating parameter indicating whether interleaving should be usedalso help to optimize the communication channel. Interleaving involvesbreaking down the data into segments which are redundantly transmittedin different hopping frames. For example, in a three segment exchange,the first and second segments are sequentially combined and sent duringa first hopping frame. In a subsequent hopping frame, the second andthird segments are sequentially combined and transmitted in a thirdhopping frame. The receiving transceiver compares each segment receivedwith the redundantly received segment to verify that the transmissionwas successful. I errors are detected, further transmissions must bemade until verification is achieved. Once achieved, the transceiverreconstructs the data from the segments.

Other methods of interleaving are also contemplated. For example, asimpler form of interleaving would be to sequentially send the datatwice without segmentation on two different frequencies (i.e., on twosuccessive hops).

As can be appreciated, interleaving provides for a redundancy check butat the expense of data or message throughput. The interleaving parameterdetermines whether interleaving is to be used and, if so, the specificmethod of interleaving.

In addition, any combination of the above frequency-hopping parametersmight interact to define an overall operating configuration, differentfrom what might be expected from the sum of the individual operatingparameters. For example, selecting interleaving and coding, throughtheir respective parameters, might result in a more complex combinationscheme which combines segmentation and error correction in somealternate fashion.

In the United States, data communication equipment operating in theultra-high frequency (UHF) range under conditions of frequencymodulation (FM) is subject to the following limitations.

1) The occupied band width is sixteen kilohertz maximum with fivekilohertz maximum frequency deviation.

2) The channel spacing is 25 kilohertz. This requires the use of highlyselected filtering in the receiver to reduce the potential forinterference from nearby radio equipment operating on adjacent channels.

3) The maximum output power is generally in the range of ten to threehundred watts. For localized operation is a fixed location, however,transmitter power output may be limited to two watts, maximum, andlimitations may be placed on antenna height as well. These restrictionsare intended to limit system range so as to allow efficient re-use offrequencies.

For non-return to zero (NRZ) data modulation, the highest modulatingfrequency is equal to one half the data rate in a baud. Maximumdeviation of five kilohertz may be utilized for a highest modulationfrequency which is less than three kilohertz, but lower deviations aregenerally required for higher modulation frequencies. Thus, at a rate often thousand baud, and an occupied bandwidth of sixteen kilohertz, thepeak FM deviation which can be utilized for NRZ data may be threekilohertz or less.

Considerations of cost versus performance tradeoffs are the major reasonfor the selection of the frequency modulation approach used in thesystem. The approach utilizes shaped non-return-to-zero (NRZ) data forbandwidth efficiency and non-coherent demodulation using alimited-discriminator detector for reasonable performance at weak RFsignal levels. However, the channel bandwidth constraints limit themaximum data “high” data rate that can be utilized for transmitting NRZcoded data. Significant improvements in system throughput potential canbe realized within the allotted bandwidth by extending the concept ofadaptively selecting data rate to include switching between sourceencoding methods. The preferred approach is to continue to use NRZcoding for the lower system data rate and substitute partial response(PR) encoding for the higher rate. The throughput improvements of NRZ/PRscheme over an HRZ/NRZ implementation are obtained at the expense ofadditional complexity in the baseband processing circuitry. An exampleof a transceiver using such an approach can be found in the previouslyincorporated patent application of Ronald L. Mahany, U.S. Ser. No.07/485,313, filed Feb. 26, 1990, now abandoned.

Partial response encoding methods are line coding techniques which allowa potential doubling of the data rate over NRZ encoding using the samebaseband bandwidth. Examples of PR encoding methods include duobinaryand modified duobinary encoding. Bandwidth efficiency is improved byconverting binary data into three level, or pseudo-ternary signals.Because the receiver decision circuitry must distinguish between threeinstead of two levels, there is a signal to noise (range) penalty forusing PR encoding. In an adaptive baud rate switching system, theeffects of this degradation are eliminated by appropriate selection ofthe baud rate switching threshold.

Since PR encoding offers a doubling of the data rate of NRZ encoded datain the same bandwidth, one possible implementation of a NRZ/PR baud rateswitching system would be a 4800/9600 bit/sec system in which thelow-pass filter bandwidth is not switched. This might be desirable forexample if complex low-pass filters constructed of discrete componentshad to be used. Use of a single filter could reduce circuit costs andprinted circuit board area requirements. This approach might also bedesirable if the channel bandwidth were reduced below what is currentlyavailable.

The implementation with bandwidth available is to use PR encoding toincrease the high data rate well beyond the 9600 bit/sec implementationpreviously described. An approach using 4800 bit/sec NRZ encoded datafor the low rate thereby providing high reliability and backwardcompatibility with existing products, and 16K bit/sec PR encodedtransmission for the high rate may be utilized. The PR encodingtechniques is a hybrid form similar to duobinary and several of itsvariants which has been devised to aid decoding, minimize the increasein hardware complexity, and provide similar performance characteristicsto that of the previously described 4800/9600 bit/sec implementation.While PR encoding could potentially provide a high data rate of up to20K bit/sec in the available channel bandwidth, 16K bit/sec ispreferable because of the practical constraints imposed by oscillatortemperature stability and the distortion characteristics of IF bandpassfilters.

All of the above referenced parameters must be maintained in localmemory at both the transmitter and the receiver so that successfulcommunication can occur. To change the communication environment bychanging an operating parameter requires both synchronization betweenthe transceivers and a method for recovering in case synchronizationfails.

In one embodiment, if a transceiver receiving a transmission(hereinafter referred to as the “destination”) determines that anoperating parameter needs to be changed, it must transmit a request forchange to the transceiver sending the transmission (hereinafter the“source”). If received, the source may send an first acknowledge to thedestination based on the current operating parameter. Thereafter, thesource modifies its currently stored operating parameter, stores themodification, and awaits a transmission from the destination based onthe newly stored operating parameter. The source may also send a “noacknowledge” message, rejecting the requested modification.

If the first acknowledge message is received, the destination modifiesits currently stored operating parameter, stores the modification, sendsa verification message based on the newly stored operating parameter,and awaits a second acknowledge message from the source. If thedestination does not receive the first acknowledge is not received, thedestination modifies the currently stored parameter, stores themodification as the new operating parameter, and, based on the newparameter, transmits a request for acknowledge. If the source hasalready made the operating parameter modification (i.e., the destinationdid not properly receive the first acknowledge message), the destinationreceives the request based on the new parameters and response with asecond acknowledge. After the second acknowledge is received,communication between the source and destination based on the newlystored operating parameter begins.

If the destination does not receive either the first or the secondacknowledge messages from the source after repeated requests, thedestination replaces the current operating parameter with a factorypreset system-default (which is also loaded upon power-up). Thereafter,using the system-default, the destination transmits repeated requestsfor acknowledge until receiving a response from the source. Thesystem-default parameters preferably define the most robustconfiguration for communication.

If after a time-out period the second request for acknowledge based onthe newly stored operating parameters is not received, the sourcerestores the previously modified operating parameters and listens for arequest for acknowledge. If after a further time-out period a requestfor acknowledge is not received, the source replaces the currentoperating parameter with the factory preset system-default (which is thesame as that stored in the destination, and which is also loaded uponpower-up). Thereafter, using the common system-default, the sourcelistens for an acknowledge request from the destination. Once received,communication is re-established.

Other synchronization and recovery methods are also contemplated. Forexample, instead of acknowledge requests originating solely from thedestination, the source might also participate in such requests.Similarly, although a polling protocol is used to carry out thecommunication exchanges described above, carrier-sense multiple-access(CSMA) or busy tone protocols might alternately be used.

In the embodiment illustrated in FIG. 1A, various modes of operation aredynamically controlled by the wireless access devices 2A-C. Such controlinvolves the consideration by each wireless access device of manyfactors such as: 1) received signal strength; 2) success/fail rates; 3)mode capabilities of participating devices; 4) neighboring access deviceoperation and performance; 5) application support required; and 6) powerconcerns. In addition to modifying the parameters of a particular mode(as previously mentioned), the wireless access devices may also selectfrom a plurality of modes (as described in more detail below inreference to FIG. 10).

FIG. 1B is a flow diagram illustrating the operation of a wirelessaccess device in accordance with present invention whereby multiplewireless devices having potentially different transceiver capabilitiesare supported. In particular, a wireless access device manages ongoingcommunication within its cell with a previously selected mode and modeparameters at a block 401. At a block 403, the wireless access deviceidentifies an attach request from a wireless transceiver (hereinafterthe “requesting transceiver”) that may have wandered into the cell. Theaccess device 403 responds at a block 405 by identifying the availablemodes of operation of the requesting transceiver. At a block 407, themodes are added to a mode table, which stores the available modes of allthe participating devices. Note that a requesting transceiver onlycommunicates the availability of those modes which are both possible(determined by the transceiver's design) and useful (determined by acurrent application).

If the requesting device is capable of operating in the currentlyselected mode, as determined at a block 409, the wireless access devicecommunicates mode information and parameters to the requestingtransceiver at a block 413. Thereafter, the wireless access devicereturns to the block 401 and services all participating devicesincluding the requesting device in the current mode with currentparameters.

Alternatively, if the requesting device has a limited number ofoperating modes, at the block 409 the current mode may not be apossibility. If the requesting device is not capable of operating in thecurrent mode, the wireless access device attempts to select a new modeat a block 411. If at least one common mode can be found, e.g., if allthe participating devices and the requesting device have at least onecommon mode, the wireless access device chooses the common mode that itbelieves will offer optimal performance. Thereafter, at a block 413, thewireless access device communicates the selected mode and parameterinformation to the requesting transceiver at the block 413 and returnsto the block 401. At the block 401, because a new mode has beenselected, the wireless access device vectors to service the event at ablock 419. At a block 421, the wireless access device broadcasts themode and parameter information, and, at a block 423, changes its ownmode. Thereafter, the wireless access device returns to service ongoingcommunication in that mode at the block 401.

If however a common mode cannot be found for a requesting transceiver atthe block 411, the requesting transceiver is rejected fromparticipating. In such a case, the customer must identify the radioscausing the limitations and upgrade them. In another embodiment, thewireless access device operates in a time shared configurations,switching between two or more modes in a sequential fashion. In thisembodiment, however, the overall delays in the system may still justifyupgrading the radio transceiver(s) causing the limitations.

During the course of ongoing operation at the block 401, the wirelessaccess device monitors channel performance (a variety of factorsdescribed in more detail above), and compares such performance toavailable other common modes of operation and considers potentialparameter modifications. In particular, as represented by the block 429,if channel conditions degrade below a predefined threshold, the wirelessaccess device vectors to consider changing modes. At a block 431, thewireless access device consults the mode table. If a new mode isavailable and warranted, per a determination at a block 433, thewireless access device responds by selecting an alternate common mode atthe block 435, resets the conditions that caused the vectoring andreturns to the block 401 to complete the mode change via the blocks 419,421 and 423. Similarly, each time a participating transceiver detachesfrom the cell (through either active detachment or aging) as representedby an event block 445, the wireless access device removes thattransceiving device's mode information from active status in the modetable and attempts to choose a better common mode via the blocks 431,433, 435 and 437. Although not shown, the wireless access device mightalso periodically attempt to choose a better common mode, withoutrequiring channel conditions to change or degrade or participants todetach.

FIG. 1C is a block diagram illustrating a radio transceiver used inwireless access devices and any transceiving device, such as a printer,code reader, hand-held terminal, etc., and built in accordance with thepresent invention to support multiple modes of operation. Thetransceiver module 501 comprises control circuitry 503, a modulator 505,a demodulator 507, and oscillator 509 and a switch circuit 511. Thecontrol module may have either an internal or external antenna attachedthereto, i.e., an antenna 513.

The control circuitry 503 manages the operation of the other componentsof the transceiver module 501. The control circuitry 503 receivesinstructions and data to be transmitted from a host unit (not shown) viaa wired communication link 515. The control circuitry 503 deliver suchdata to the modulator 505 for modulation (and possibly spreading).Thereafter, the data is delivered to the antenna 513 via the switch 511.Data and control signals received by the antenna 513 passes through theswitch 511 to the demodulator 507 for demodulation (and possiblydespreading). The control circuitry 503 receives the demodulated data orcontrol signals for processing and/or delivery to the host unit throughthe link 515.

The control circuitry 503 causes the selection of operating parametersand modes as described previously and in reference to FIG. 1B.Specifically, the control circuitry 503 sets the configuration of themodulator 505, demodulator 507 and oscillator 509. For example, tooperate in a direct sequence spread spectrum mode, the control circuitry503: 1) sets the base frequency of the oscillator 509; 2) sets relatedmode parameters such as the chipping rate; and 3) delivers enablesignals and a spreading code to a spreader circuit 516 and despreadercircuit 517 of the modulator 505 and demodulator 507, respectively. Tooperate in a frequency hopping mode, the control circuitry 503: 1)establishes related parameter settings; 2) disables the spreading anddespreading circuits 516 and 517; 3) selects a hopping sequence offrequencies; and 4) directs the oscillator 509 through the sequence. Tooperate in a hybrid, direct sequence, frequency hopping mode, thecontrol circuitry 503: 1) establishes related parameter settings; 2)delivers enable signals and a spreading code to a spreader circuit 516and despreader circuit 517; 3) selects a hopping sequence offrequencies; and 4) directs the oscillator 509 through the sequence.Similarly, the control circuitry 503 may select any modes, e.g., themodes identified in reference to FIG. 10 below, and set all parametersrelated thereto.

FIG. 1D is a block diagram illustrating the operation of the wirelessaccess device having the multi-mode transceiver of FIG. 1C installedtherein. In particular, a transceiver module 501 (as described inrelation to FIG. 1C) is installed within a wireless access device 523.The wireless access device 523 contains control circuitry 525 andinterface circuitry 527 for communicating with a wired network 529. Inaddition to providing typical access device service, the controlcircuitry 525 of the wireless access device 523 manages all mode andparameter changes for the transceiver module 501. The control circuitry525 monitors, among other factors, the historical performancecharacteristics of each mode, neighboring access device modes,parameters and performance and current mode performance (via receivedsignal strength indications and success/failure rates). The controlcircuitry 525 also maintains and updates the mode table, attachment anddetachment of participants, as described above in reference to FIG. 1Bfor example. The control circuitry 525 performs such functionality viacontrol signals delivered to the control circuitry of the transceivermodule 501.

When installed in a portable/mobile or stationary transceiver unit(e.g., peripheral device, code reader, hand-held terminal, etc.), atransceiver module responds to communication control through commandsreceived from the wireless access device while attempting to attach.Such commands direct the mode and parameters of operation of thetransceiver module in the transceiver unit. In addition, the controlcircuitry of the transceiver module 501 directs entry of a default modeand default parameters prior to receiving direction from a wirelessaccess device. Although the transceiver module 501 may receiveadditional mode and parameter commands from the host controller withinthe transceiver unit, it need not do so. Such local control by atransceiver unit, however, may prove advantageous in other wirelessnetwork embodiments or in specific applications. For example, othernetwork embodiments might involve only two transceiver units without awireless access device. As such, the transceiver units may negotiate amode and related parameters amongst themselves, controlling such changesvia host processors within the transceiver units. Negotiation of modeand parameter changes might also involve channel condition monitoring orother factors currently assigned to the wireless access device.

FIG. 2A illustrates a hand-held portable data terminal whichincorporates the present invention, designated generally by the numeral10. The data terminal 10 may be one of several data terminals in a localarea network which utilizes radio frequency (RF) communications for datatransfer. The data terminal 10 illustrated is a mobile data unit thatincludes a radio transceiver unit incorporating the present invention.Of course, as has been previously described, the present invention maybe incorporated into stationary units as well as mobile units. Further,the stationary units may comprise wireless access points, other functionperforming devices such as printers, stationary scanners, or otherdevices. Moreover, mobile units incorporating the present invention neednot comprise the hand-held radio format illustrated in FIG. 2A. Themobile units could be installed in vehicles, worn by a user, orinstalled in any other fashion that causes the device to be mobile.

The data terminal 10 includes an antenna 12 is disposed at the top end14 of the data terminal for radio frequency transmission and reception.The data terminal may include a display screen 16 for displaying programinformation and for interfacing the operator with the data terminal 10.The display screen 16 may be a reflective super-twist liquid crystaldisplay (LCD), for example. The data terminal 10 may include a keypad 18having a plurality of keys for entering data into the data terminal 10and for control of the data terminal 10 by the operator.

FIG. 2B shows the data terminal 10 of FIG. 2A which includes a module inwhich circuitry for accomplishing the present invention is disposed. Thedata terminal 10 has a modularly attached radio module 20 which alsocontains scanning circuitry in addition to radio circuitry. The antenna12 of FIG. 2A is affixed to the radio/scanner module 20 and may be atype suitable for portable battery powered electronic devices. Theradio/scanner module 20 has an extended outer shell 24 in order tocontain both the radio and the scanner circuitry. A button 26 may bedisposed on either or both sides of the radio/scanner module 20 toactivate the scanning circuitry and scan encoded data, such as thatcontained in a bar code or two dimensional image. The module 20 could,in another embodiment, include a digital camera or other functionalequipment. As illustrated, the radio/scanner module 20 is constructed tobe modularly received by a recession 28 in the data terminal such that acontinuous unit is formed by attaching the module 20 to the dataterminal.

FIG. 3 shows a side view of another embodiment of a data terminal 10with an alternate modular radio module attached thereto. The module 30includes a radio incorporating the teachings of the present inventionbut does not include the image capture electronics of the radio/scannermodule 20 of FIG. 2B. Because the module 30 is more compact than radioscanner module 20 of FIG. 2B, the body of radio module 30 is generallyflush with the body of the data terminal 10 when attached thereto.

FIG. 4 shows a data terminal 10 that is removably attachable to theradio/scanner module 20 of FIG. 2B. The motion required for attachmentof the module 20 to the data terminal 10 generally follows the directionof line 32. The module 20 is positioned toward the terminal 10 and thenlocked into place by a downward movement. L-shaped latches 34 may beused to removably secure the module 20 to the terminal 10.

FIGS. 4A, 4B and 4C illustrate in detail the cooperation between a radiomodule and the hand-held portable data terminal shown in FIG. 3. Theradio module 30 houses a radio unit 340. An antenna connector 342connects to antenna connector pins 344 at an end of the radio unit 340to provide electrical connection to an antenna which may be internallyor externally mounted on the module 30. An array of connecting pins 346preferably connect the radio unit 340 to the data terminal which mayhave a receptacle for receiving the connecting pins 346. The radiomodule 30 may include a hand strap 348, one end of which being connectedto the module 30 and the other end being connected to the terminal 10,to facilitate manipulation of the terminal 10 in one hand and to preventaccidental dropping, for example.

FIG. 5 depicts another type of hand-held portable data terminal 36 thatincorporates the present invention and that is designed to receivestandard PCMCIA computer feature card modules. The terminal 36 may havea module carriage housing 38 which may receive various types of PCMCIAcards 40: Type I (3.3 mm in thickness), Type II (5.0 mm in thickness) orType III (10.5 mm in thickness) PCMCIA sized modules for example.

FIG. 6 shows the data terminal of 36 of FIG. 5 having a rotatablyextendible and retractable carriage housing 38. The carriage housing 38is shown in the extended position holding a Type III PCMCIA module 42which may, for example, contain the radio circuitry of the presentinvention.

FIG. 7 is an exploded view of the internal components of a radio module30 of the present invention such as the module 30 of FIG. 3. Thecircuitry of radio module 30 of the present invention such as the module30 is preferably mounted on a circuit card assembly (CCA) board 44containing, for example, the transmitter and receiver electroniccomponents (not shown). The radio CCA 44 may have metallic coverings, orcans (not shown), soldered to the board over critical radio componentsto provide two-way electromagnetic shielding to reduce or eliminateradio frequency interference.

In embodiment of FIG. 7, the radio module CCA 44 is contained within ametallic radio cover 46 to provide electromagnetic shielding of theradio CCA 44. The radio CCA 44 and radio cover 46 may be attached to amounting frame 48 which provides supporting structure for the internalcomponents of the radio module 30. Radio cover 46 and mounting frame 48may be fabricated of ABS type plastic or of a conductive metal toprovide electromagnetic shielding. The radio CCA 44 and the radio cover36 may be attached to the mounting frame 48 by a plurality of fasteners50 which may be four #2 screws in a preferred embodiment.

An internal antenna 52 may be connected to the radio circuitry of theradio CCA 44 in lieu of the external linear antenna 12 shown in FIG. 2Aand completely contained within the radio module 30. The radio module 30may utilize the antenna means of U.S. Pat. No. 5, 322,991 issued Jun.21, 1994 and assigned to NORAND Corporation of Cedar Rapids, Iowa, theassignee of the present application, Said U.S. Pat. No. 5,322,991 ishereby incorporated by reference in its entirety. The antenna 53 maycomprise a quarter-wavelength single loop of wire of approximately 83 mmfor transmissions near 900 MHz. When the loop antenna 52 is driven bythe output of the radio module 44, a uniform circulatory current flowingthrough the antenna 52 results in a radiation pattern similar to that ofa magnetic dipole. The antenna 52 preferably has a nominal impedance of50S.

An internal shield 56 may be utilized and inserted between the radiocircuit card assembly (CCA) 44 and the radio interface card (RIC) 58which contains the electronic circuitry necessary6 to interface theelectronics of the radio CCA 44 with the electronics of the dataterminal 10 of FIG. 2A. The radio interface card 58 may be a type usedfor a 2.4 GHz radio since the interface to the radio CCA 44 is baseband.The 900 MHz radio 44 of the present invention may be designed to appearas a 2.4 GHz radio accepting the same frequency control inputs andemploying the same media access control protocols as a 2.4 GHz radio.

Electrical connectors 60 may be mounted at an end of the radio interfacecard 58 for providing electrical connection to the CPU board (not shown)of the portable data terminal with which the radio module 30 isutilized, such as terminal 10 of FIG. 2A. A mounting fastener 62, whichmay be a screw, fastens the radio interface card to the radio moduleassembly 30. An acoustic-electric transducer such as buzzer 64 may beincluded with the radio module 30 and electronically connected to theradio CCA 44 5to provide the operator with audio information and cues,for example a beep or buzz when the radio module 30 is powered on. Framemounting screws 66 may be utilized to fasten the assembly to the outershell 68 via mounting frame 48. The entire module assembly may bewrapped in a metallic foil to provide electromagnetic shielding to theradio module 30. The outer shell 68 is preferably a type of ABS plasticand is formed to modularly and contiguously fit the recession 28 of thedata terminal 10 as shown in FIG. 2B.

FIG. 8 is an exploded view of the radio/scanner module 20 illustrated inFIGS. 2B and 4. The components and assembly thereof of the radio/scannermodule 20 are substantially similar, with some slight modificationsthereof where necessary, to that of the radio module 30 of FIG. 7, theprinciple difference being the addition of scanner circuitry in theradio/scanner module 20 for reading optically readable data files suchas standard bar codes. The radio/scanner module 20 includes radiointerface card 58 with electrical connectors 60, mounting frame 48,internal shield 56, radio CCA 44, antenna 52, radio cover 46, and buzzer64 as shown in FIG. 7 (and as described in the discussion of FIG. 7).

In addition to the above components, the radio/scanner module 20includes a scanner printed circuit board 70 on which the scannerelectronic circuitry are mounted. A flex circuit connection assembly 72may be utilized to interconnect the electronic circuitry, such as thecircuitry of scanner card 70 and interface card 58. The outer shell 74of the radio scanner module is substantially similar to the outer shell68 of radio module 30 as shown in FIG. 7, modified to accommodate theadditional components of the radio/scanner module 20.

A rubber nose end cap 76 may be attached to the forward end of the outershell 74 for providing impact shock absorption and protection. A seallabel 78 may be used to provide an adhesive seal between rubber nose endcap 76 and outer shell 74. A lens 80 mounted with a lens seal support 82may be disposed in the rubber end cap 76 to provide a sealed lightaperture for the scanner circuitry. Scanning of an optically readabledata file may be controlled with a scam button 86 which covers am inputkeyboard and elastomer 84 and is supported by a scan button bezel 88mounted in a button aperture 90 on a side of the outer shell 74. Theradio/scanner may have a plurality of scan or input buttons 86. Forexample, an additional button may be provided on the side of the outershell 74 opposite the button 86 shown in FIG. 8.

Frame mounting screws 92 are provided to mount the mounting frame 48containing the module assembly to the outer shell 74. The outer shell 74and radio/scanner module are formed to modularly and contiguously attachto the data terminal 10 as illustrated in FIGS. 2B and 4 in a mannersubstantially similar the attachment of radio module 30 to data terminal10. The entire module assembly 20 may be wrapped in a metallic foil toprovide electromagnetic shielding to the radio module 20.

FIG. 9 is an exploded view of the PCMCIA Type III radio module 42 ofFIG. 6. The PCMCIA radio module 42 may also be constructed within asmaller sized PCMCIA module such as Type II or Type I enclosure bycombining the circuitry of the radio interface card 58 and the radiocircuit card assembly 44 on a single printed circuit board, for example.The PCMCIA radio module 44 may contain the radio circuit card assembly44 and the radio interface card 58 of FIGS. 7 and 8. The radio interfacecard 58 is preferably adapted to conform to PCMCIA device interfacestandards for utilization in PCMCIA radio module 42. The circuitry ofthe radio CCA 44 and the radio interface card 68 may be interconnectedby a board to board connector 94. Alternatively, all of the circuitry ofthe RIC 58 and the CCA 44 may be combined on a single printed circuitboard for smaller sized radio modules (20, 30 or 42).

Standoffs 96 may be soldered directly to the radio interface card 58 andare provided to separate the radio CCA 44 from the radio interface card58 and to provide attachment thereto with fasteners 98 (preferably #2-56screws). The screws 98 preferably attach the radio CCA 44 to a customPCMCIA Type III frame 100 which provides structural support andprotection of the circuit boards 44 and 58. A PCMCIA electricalreceptacle 102 may be provided to electrically connect the radio moduleto standard PCMCIA connectors in the electronic equipment in which themodule 42 is to be utilized, such as the data terminal 36 of FIGS. 5 and6.

An antenna connector 104 may be mounted on the radio CCA 44 forconnection of the module to an antenna which may be, for example, theantenna 12 of FIG. 2A, the antenna 52 of FIGS. 6 and 7 of the antennameans of U.S. Pat. No. 5,322,991 issued Jun. 21, 1994 incorporatedherein. Alternate antenna clips 106 may be utilized for adapting theradio module 42 to various antenna connection configurations.

The PCMCIA radio module 42 may be contained within top and bottom covers108 and 110 respectively which are preferably comprised of tin platedcold rolled steel. The module covers 108 and 110 may provide two wayelectromagnetic shielding of the radio frequency circuitry. When theradio module 42 is assembled and contained within top cover 108 andbottom cover 110 the module preferably conforms to PCMCIA Type IIIdimensions. The module 42 may also be adapted to conform to PCMCIA TypeII or Type I dimensions as well.

The transceiver module as shown in FIG. 9 may be utilized in a standarddesktop or portable computer such as a laptop computer which is designedto utilize standard PCMCIA computer modules. The portable computer maybe implemented as part of a multilayered communication network such as acommunications node to communicate, for example, with several dataterminal in a connected wired network, as well as with nodes in thewireless network. In this fashion, the computer could serve as awireless access point, a wireless access server, or another type ofwireless device providing access to the wireless network. A preferredembodiment of the present invention implements Layer 1 (the physicallayer) and the medium access control (MAC) sub-layer of Layer 2 (thedata link layer) of the International Standards Organization ReferenceModel (ISORM) operating under an ODI or NDIS driver. A driver interfaceto the MAC sub-layer allows the utilization of industry standardmulti-layer communications protocol above the MAC sub-layer.

FIG. 10 is a functional block diagram of an embodiment of the radiomodules 20, 30 and 42 of the present invention. The components of FIG.10 implement the teachings of the present invention by causing the radiomodule to be operable in any of a plurality of spread spectrum modesdepending upon system and transmission conditions. The componentsillustrated could be found in a mobile unit or a stationary unit toprovide equivalent functionality in the units. In one embodiment, atleast one stationary unit and a plurality of mobile units in a wirelesslocal area network are capable of operating in a plurality of spreadspectrum modes such as direct sequence, channelized direct sequence,frequency hopping, channelized frequency hopping, or hybrid modes. Thecomponents illustrated in FIG. 10 allow the radio modules to operate insuch a fashion.

The antenna section includes an antenna 112 for transmitting andreceiving radio frequency energy. The antenna 112 may be one of theantennas described in the discussion of FIGS. 7, 8 and 9. The radiocircuitry corresponds to the radio circuitry of the radio CCA 44 ofFIGS. 7, 8 and 9 and contains the receiver circuitry 114, thetransmitter circuitry 118 and the frequency generator (“FREQ.GENERATOR”) 116.

The radio frequency (RF) transceiver 298 of the present inventioncomprises a receiver 114 and a transmitter 118. The transmitter 118preferably comprises a data formatter and spreader (“BASE BANDFORMATTER/SPREADER”) 124, a selectable transversal filter 150 comprisingprogrammable transversal filters (“PROGRAMMABLE TRANSVERSAL FILTER”) 146and 148 (See FIG. 11), a binary phase shift keying (BPSK) modulator(“BPSK MODULATOR”) 130, and a transmitter up converter and lineartransmit power amplifier (“TX UP CONVERTER & AMP”) 314. The receiver 114preferably comprises a receiver down converter 304, a selectablebandwidth intermediate frequency (IF) stage (“SELECTABLE BW IF”) at afixed IF center frequency, a non coherent I/Q base band converter(“BASEBAND CONVERTER”), and a demodulator/despreader (“DEMOD.DESPREAD.”).

A common radio frequency bandpass filter (“BPF”) 399 is shared by boththe transmitter 114 and the receiver 118. The transceiver 298 is coupledto an antenna 112 through an antenna switch circuit 302. A frequencygenerator 116 is common to both the receiver 114 and the transmitter118, producing a frequency agile main VCO output (“MAIN VCO”) 196, andan auxiliary output (“AUX VCO ”) 334 at twice the IF frequency. Adivided by 2 circuit (316 and 318) in the transmit path of the auxiliaryVCO signal 334 is activated when the transceiver 298 is switch to thetransmit mode.

The transmit operation the media access control (MAC) microprocessor(“MAC μP”) 128 enables the various transmit circuits through the controlbus (see CONTROL of FIG. 18). In particular, however, the MAC μP 128controls the various components illustrated in FIG. 10 as illustrated.However, in other embodiments of the present invention, the MAC μP 128may control only a portion of the components or even more of thecomponents. To implement the teachings of the present invention, the MACμP 128 controls the various elements illustrated in FIG. 10 so as toperform transmission and reception in any of the various spread spectrummodes. In order to accomplish such various modes, the MAC μP 128 mustcontrol the frequency generator 116 to cause modulation over all of aspreading bandwidth via variations in the MAIN VCO frequency. Inaddition, the MAC μP 128 provides control to the modulator 130, RECEIVERDOWN CONVERTER 304, TX UP CONVERTER & AMP 314, the SELECTABLE BW IF 322,the MODULATOR 130, the SELECTABLE TRANSVERSAL FILTER 150, theDEMODULATOR DESPREADER 184, and the FORMATTER/SPREADER 124 in order tocause the circuitry to perform in the various spread spectrum modes.

As is known, each of the various spread spectrum modes requirespackaging, modulating, transmitting, and receiving data in particularformats and frequencies. Thus, the MAC μP 128 provides control over theelements illustrated in FIG. 10 in a fashion so as to enable each of thevarious spread spectrum modes. Techniques known in the art may beemployed to cause the components illustrated in FIG. 10 to perform inparticular spread spectrum modes.

The functions of the baseband formatter/spreader 124 may be contained ina digital application-specific integrated circuit, or ASIC, (not shown)with circuitry configurable to the desired transmission mode by thecontrol microprocessor 128. The ASIC preferably produces a clock at thecorrect data rate for the selected mode which is used to time serialtransfer of a data frame from the transmit data output of the MAC μP 128(see TXD of FIG. 18).

In the direct sequence (DS) modes, the data is mapped into I/Q symbolsfor either BPSK or QPSK modulation. The ASIC generates a synchronouschip clock at a multiple of the symbol rate that is applied to thepseudo-random number (PN) generator of FIG. 14A to produce a chippingsequence at the selected spreading ratio. The exact chipping sequence isselected by programming the feedback select of FIG. 14A. The chippingsequence is multiplied with the I/Q data symbols by use of exclusive ORgates. The selected data rate and spreading ratio determine the mainlobe bandwidth of the transmitted signal. The bandwidth of the main lobeand side lobes are reduced by applying the transversal filters (146 and148 of FIG. 14B), which comprise circuitry of the transversal filter 150of FIG. 10 with the shift registers operating at the chipping raterather than the symbol rate. The main lobe bandwidth is limited toapproximately 1.6 times the chip clock frequency.

The remainder of the Transmitter 118 is a standard I/Q modem. The I/Owaveforms are applied to a quadrature PSK modulator operating at ½ theAuxiliary VCO frequency. The modulated signal is filtered to reduceharmonic content, then undergoes a second conversion with the Main VCOoutput 196 to produce a final output frequency. This signal is filteredto reduce the image of the mix product from this second conversion, andthen amplified by the antenna 112 through the antenna switch 302 and RFbandpass filter 300.

In the receive mode, the receiver circuitry 114 is switched on and thetransmitter circuitry switched off through the control interface.Incoming signals present at the antenna are amplified and converted tothe IF frequency by mixing with the main VCO output 196. The output ofthe receiver down converter 304 is applied to the selectable bandwidthIF filter 322, which is programmed to the correct bandwidth for theselected mode of operation by the MAC μP 128. The filters 174, 176 and178 provide rejection of out of band signals for the selected signalbandwidth.

The filtered output is applied to a limiting amplifier, then to the I/Qbaseband converter 312. The limiter 182 produces a received signalstrength indication that is proportional to log of the signal energy inthe IF. This is applied to an A/D converter 126 then to the control μP128. This function is useful for detecting proximity to the transmittingunit, or to an interferor, and is also useful as an OOK detector.

The baseband converter 312 contains an internal divide-by-two circuitwhich produces a carrier at ½ the Auxiliary VCO frequency which is alsoat the nominal IF frequency. This is mixed with the limited IF signal toproduce baseband I/Q waveforms. These in turn are applied to comparatorsthat serve as hard decision circuits, then to the correlator 330 (seeFIG. 17) within the ASIC.

The frequency generation system 116 must be programmed to produce theMain VCO output. A serial interface within the control bus provides thiscapability. In the DS modes the Main VCO is programmed to the correctchannel frequency and remains there until a mode change or the need toavoid interference is detected. For wideband DS operation, The Main VCOis programmed to the center of the frequency range.

For FH or hybrid operation, i.e., frequency hopping combined with directsequence operation, the Main VCO is periodically reprogrammed to providethe hopping function. The MAC μP 128 maintains a timer, and table ofchannels representing the hop sequence. When the timer expires, the MACμP initiates the hop to the next frequency in the sequence. Framespassed between the various devices within the WLAN establish sharedtiming references so that all units hop in synchronism.

The MAC μP 128 provides mode control, host interface, transmit framegeneration, channel access control, receive frame processing, retries oferred packets, power management of radio circuitry, and frequencyhopping control. The frequency hopping control is a superset of theremaining functions, allowing common programming of the remainingfunctions for both DS and FH.

The host interface for the PCMCIA version is compliant with the PCMCIAphysical interface. The software interface is structured to comply withthe factory industry standards NDIS and ODI formats.

Data to be transmitted is sent via a bus 131 to the MAC circuitry 128from a host unit. The data to be transmitted is be modulated by themodulator 130 and frequency controlled by the spreader 124 according tothe particular spread spectrum transmission mode to be utilized. Thespreader 124 receives a chipping clock input that is at a frequencymultiple of the source data frequency. The output of the spreader 124 issent to the transmitter up converter and amplifier 314 to transmit theRF data signal through the antenna 112.

The radio modules of the present invention may utilize several modes ofspread spectrum RF data transmission. In one embodiment of the presentinvention, the various modes can be user selectable depending upon theparticular application in which the radio modules are to be utilized. Inanother embodiment, the modes of operation are be automatically anddynamically selected, e.g., by the MAC μP 128 based upon criteriapreviously described. Such selection might also be performed by or withthe assistance of the terminal unit or a digital signal processorprovided for such task.

In a particular example, a microprocessor in the host terminal mayretrieve stored modes of operation utilized on the previous day to whicha higher logical multiplier is used to determine which transmission modeor modes are to be selected for that day's data transmissions.Additionally, data such as the average signal strength, most frequentlyutilizes transmission mode, the average level of interference and noisefor a particular mode or transmission success rate (e.g. percentages oftransmissions) may be saved in nonvolatile memory and factored into themode selection routine.

A description of particular spread spectrum modes follows in Table 1.The modulation techniques as described in Table 1 may be directsequencing (DS), frequency hopping (FH) or on-off-keying (OOK) or acombination thereof. The rate at which data may be transmitted is givenis kilobits per second (kb/s) and the channel bandwidth is given foreach mode for the operational frequency range of 902 to 928 MHz. Thefull bandwidth of an embodiment of the radio is 26 Table 1.

TABLE 1 Spread Spectrum Transmission Modes MODULATION DATA MODETECHNIQUE RATE BANDWIDTH 1 DS 250 kb/s full band 2 CHANNELIZED 250 kb/s5 channel DS 5 MHz 3 DS 500 kb/s full band 4 FH 250 kb/s 50 channels 500kHz 5 FH/DS  10 kb/s 50 channels 500 kHz 6 OOK 19.2 kb/s  50 channels500 kHz 7 DS  10 kb/s 50 channels 500 kHz

The various spread spectrum modes are utilized to obtain optimumperformance for particular modes of operation of the data terminal. Theradio of the present invention preferably has a transmission range of upto 300 feet for closely spaced interior surfaces and up to 1300 feet inopen spaces resulting in an operational coverage area from 280,000 to5,300,000 square feet.

Utilization of the various transmissions modes results in variableimmunity of the data signals from RF interference. The data terminal inwhich the radio is utilized thereby has the ability to extract the bestsystem performance in every application regardless of multipath signallevels, interference levels and the sources thereof. The data terminalalso thereby has the ability to dynamically trade data rate in returnfor coverage range (coverage range being a function of process gain)without the need to change radio hardware. Although not shown, capableof operating in the 2.4 GHz circuitry of FIG. 10 or other frequencyranges. Multiple intermediate frequency filter topology may beimplemented to achieve interference rejection via varying filterselectivity.

MODES 1 and 3 are full band direct sequence and provide no inbandinterference protection other than high process gains of 18.7 dB and15.7 dB respectively. Out-of-band protection from cellular transmissionsoperating in the vicinity is provided. MODE 1 provides good coveragearea and rejection of multipath signal. MODE 3 provides shorter coverageare in return for a high speed data rate.

MODE 2 is a channelized direct sequence mode having a process gain of 17dB. A single direct sequence cordless telephone operating in thevicinity will not degrade performance on at least four of the channels.MODE 2 provides a reasonable coverage area and jammer avoidance withchannelization.

MODE 4 utilizes full band frequency hopping having a process gain of17.1 dB. A single direct sequence cordless telephone will not degradeaverage throughput by more than 10 percent. MODE 4 provides moderatecoverage area and high system capacity with dynamic jammer immunity withfrequency hoping.

MODE 5 is a direct sequence mode which is frequency hopped having aprocess gain of 37 dB. A single direct sequence cordless telephoneoperating in the vicinity will not degrade average throughput by morethan 10 percent. MODE 5 provides a long and high coverage area anddynamic jammer immunity with frequency hopping in return for a low datarate.

MODE 6 is an on-off-keying (OOK) modulation mode having a process gainof 0 dB. MODE 6 may be utilized as a low speed, low power link to anearby scanner or printer for example.

MODE 6 the transceiver module is intended to communicator withperipheral devices containing simple AM transceivers. The Main VCO isset to the center frequency of the peripheral AM receiver. For OOKtransmission, the data formatter is configured to produce a CW outputsignal. OOK signaling is providing by strobing the enable line on thetransmitter, shown in FIG. 16.

For OOK reception, the Main VCO is set to receive at the AM transmittercenter frequency. The RSSI output from the limiting amplifier is usedfor AM detection. The signaling rate is limited by the speed at whichthe A/D can quantize the RSSI (preferably sampling several times persymbol), and at which the MAC μP 128 can process the sampled data toextract the modulation.

MODE 7 is a channelized direct sequence mode having a process gain of 20dB. A single cordless telephone operating in the vicinity will notdegrade performance on more than nine of the channels.

Other modes may also be included other than those listed above. Otherpossibly included modes may be variations or new combinations of theabove modes or modes utilizing different modulation techniques andfrequencies such as other standard RF transmission techniques which maybe contemplated by the present invention. For example, an additionalmode in an alternative embodiment may include voice communicationstransmissions utilizing standard audio modulation techniques achieved byswitching channels or transmissions modes. Using voice communicationsthe transceiver module may allow data terminal operators of amulti-level radio-frequency communications network to verballycommunicate with one another or their supervisors throughout the entirenetwork. Voice and data communications may be utilized with a singleportable battery powered electronic device rather than having a dataterminal for data communications and a separate mobile radio for voicecommunications, for example. Similarly, the process gains, samplingrates, etc., are exemplary value which may be modified as provesdesirable.

FIG. 11 is a conceptual block diagram of the operation of thetransmitter of FIG. 10 when operating in a direct sequence spreadspectrum transmission mode. As illustrated, in the operation, data isreceived by the BASE BAND FORMATTER/SPREADER which, based upon theCONTROL SPREADER signal received from the MAC μP 128, spreads the codebased upon a particular code spreading sequence or pattern. The BASEBAND FORMATTER/SPREADER provides data on two output paths so that thedata may be modulated according to the BPSK modulation scheme. Thespread code is then processed by a programmable transversal filter 150having two separate filters, 146 and 148, one for each data path. Oncefiltered, the data is modulated by the components 136, 138, 140, 320,and 142 of the BPSK modulator. From the BPSK modulator, the dataproceeds until it is transmitted.

FIG. 12 shows a conceptual diagram of the operation of the receiverutilized in conjunction with the transmitter of FIG. 11. In theembodiment, data received by the antenna 112 passes through azero-degree phase shift block 152. From the block, one path goesdirectly to one input of a multiplier 158 while the second path passesthrough an RF DELAY block 154 and then passes to a second input of themultiplier 158. DELAY CONTROL is supplied to the RF DELAY block 154 bythe MAC μP 128 dependent upon the frequency of the received signal tocause a desired phase shift. From the multiplier 158 the signal passesthrough a baseband data filter 160 then through X² block 162 prior toits furthered processing.

FIG. 13 is a block diagram of the receiver 114 of the present invention.The receiver 114 may be located on the radio card CCA 44 of FIGS. 7, 8and 9. Wideband filter 170 provides additional interference protectionin the narrow band modes. A preselector filter 164 receives an RF datatransmission signal from the antenna 112 (not shown). The preselectorfilter 164 may be a two pole bandpass filter (BPF) designed to have awide bandwidth to keep the insertion loss low. In an exemplaryembodiment filter 164 has a center frequency of 915 MHz, a bandwidth of26 MHz and an insertion loss of 3.5 dB. However, the filter 164 could becontrollable as well based upon desired filtering characteristics.

The output of the preselector filter 164 is fed into two low noise RFamplifiers (LNA) 166 and 168 each of which preferably has a gain of 10and a noise figure of 2.2 dB. The gain of the RF amplifies 166 and 168is sufficient to overcome any noise which may be present on the input RFdata signal. The amplified signal may be sent to a bandpass filter (BPF)170 for additional preselection filtering. Bandpass filter 170 ispreferably designed to have four poles to provide high stop bandrejection of possible signal images present in the data signal, havingdesign values of 915 MHz center frequency, bandwidth of 26 MHz and aninsertion loss of 3.5 dB. Bandpass filter 170 could also be controlledto provide desired filtering characteristics.

The output of filter 170 is sent to the input of a mixer (“MIXER”) 170which mixes the data signal with the output 332 from the main voltagecontrolled oscillator of the frequency generator circuitry 116 of FIG.10 which preferably has an output frequency of 844 MHz. The output ofthe mixer 172 is passed through an additional bandpass filter 174 havinga center frequency of 71 MHz, a 26 MHz bandwidth and insertion loss of2.0.

The data signal is passed through an intermediate frequency selectablebandwidth filter 322 comprising filters 174, 176 and 178 for signal path180, which varies the filtering of the data signal according to thevarious modes of operation. Bandpass filter 176 is utilized for MODE 2operation and has a bandwidth of 5 MHz and an insertion loss of 8 dB.MODES 1 and 3 utilize a direct signal path 180 with an overall bandwidthof 26 MHz from the output of filter 174. MODES 4, 5, 6 and 7 utilizebandpass filter 178 which has a bandwidth of 500 kHz and an insertionloss of 8 dB. Multiple intermediate frequency filter topologies may beimplemented to achieve interference rejection via varying filterselectivity.

The data signal is fed into an intermediate frequency amplifier (IF) 182to overcome the losses from the filters. The IF amplifier 182 is a highgain amplifier having a gain and a noise factor of 7 dB. The output ofthe IF amplifier 182 drives the demodulator 181 which also receives theoutput from the auxiliary voltage controlled oscillator of the frequencygenerator circuitry 116 of FIG. 10 which may operate at a frequency of142 MHz. The demodulator 184 may have data signal products I and Q whichare fed into the inputs of the despreader circuitry 120 of FIG. 10. Thereceiver 114 may have a noise figure of less than 7 dB, an imagerejection figure of 60 dB and adjacent channel rejection of 40 dB.

FIGS. 14A and 14B are diagrams illustrating the operation of thepseudo-random number generator circuitry (“PN GENERATOR”) 122 of thetraverse filter 150 of FIG. 10. The pseudo-random number generatorcircuitry 122 is preferably located on the radio interface card 58 ofFIGS. 7, 8 and 9. The pseudo-random number generator 122 produces apseudo-random binary output which is mixed with the data signal code inorder to minimize the rate distortion for a given number of bits used torepresent the data signal. The PN generator 122 may be comprising an8-bit shift register (“8-BIT SHIFT REGISTER”) 186 utilizing a feed backselector control (“FEEDBACK SELECT”) 188 which provides programmablefeedback. A restart control device (“RESTART CONTROL”) 190 may beutilized to provide a programmable restart interval and a programmablerestart vector. The PN generator 122 is preferably controlled by acontrol input (“CONTROL”) from the MAC circuitry 128 of FIG. 10 andproduces a PN code output signal (“PN CODE”).

In the frequency hop (FH) mode, data is converted to an I/Q format forminimum shift keying (MSK) modulation. Narrowband modulation ispreferably employed so the spreader function may disabled. The powerspectral density of MSK modulation exhibits a main lobe bandwidth ofapproximately 1.5 times the symbol rate, but also contains substantialenergy in the side lobes. This energy might create interference to otherin-band or out of band systems and may also degrade operation if severalfrequency hopping sequences are used for increased throughput ormultiple access. To reduce side lobe energy, transversal filtering isemployed in the I/Q modulation paths. These consist of shift registersclocked at the symbol rate or a multiple thereof. The digital outputsfrom the shift registers are summed using a weighted resistor ladder(350 and 352) is external to the ASIC and constitutes the interfacebetween digital and analog processing.

In the direct sequence (DS) modes, the data is mapped into I/Q symbolsfor either BPSK or QPSK modulation. The ASIC generates a synchronouschip clock at a multiple of the symbol rate that is applied to thepseudo-random number generator 122 to produce a chipping sequence at theselected spreading ratio. The exact chipping sequence is selected byprogramming the feedback select 188. The chipping sequence is multipliedwith the I/Q data symbols by use of exclusive OR gates (324 and 326).The selected data rate and spreading ration determine the main lobebandwidth of the transmitted signal. The bandwidths of the main lobe andside lobes are reduced by applying the transversal filters (146 and 148)with the shift registers operating at the chipping rate rather than thesymbol rate. The main lobe bandwidth is preferably limited toapproximately 1.6 times the chip clock frequency.

FIG. 15 is a block diagram illustrating the frequency generatorcircuitry 116 of FIG. 10. The frequency generators 116 are preferablylocated on the radio card CCA 44 of FIGS. 7, 8 and 9. The radiointerface card 58 of FIGS. 7, 8 and 9 may provide data signals (“DATA”,“CLOCK”, “STROBE” and “LOCK DET”) 190 and a clock signal (“CLOCK”) 192which is preferably a 30 MHz clock to the fractional number frequencyagile synthesizer (“FRACTIONAL N SYNTHESIZER”) 194. The 30 MHz clocksignal may be divided to produce frequencies of which 30 MHz is amultiple. The synthesizer 194 may also receive frequency input signalsfrom a main voltage-control oscillator (MAIN VCO) 196 and from anauxiliary-voltage controlled oscillator (AUXILLARY VCO) 198. Thesynthesizer 194 preferably switches between transmission and receivingmodes in 200:s or less.

The main VCO 196 preferably operates at a nominal frequency of 844 MHzwhile the auxiliary VCO 198 preferably operates at a nominal frequencyof 142 MHz. The synthesizer 194 has loop filter feedback paths 200 and202 to oscillators 198 and 196 respectively for control of the frequencyof the outputs of the oscillators 196 and 198. The main VCO 196 suppliesa signal to the down converter mixer 172 of the receiver 114 of FIG. 13and provide a signal to the modulator 206 of the transmitter 118 of FIG.11 after being fed through a divide by 2 circuit (“DIVIDE BY 2”) 204.

FIG. 16 is block diagram illustrating the functionality of thetransmitter circuitry 118 of FIG. 10. The transmitter 118 is located onthe radio card CCA 44 of FIGS. 7, 8 and 9. The transmitter 118 receivesdata signal input products I and Q from the modulator and spreadercircuitry 124 and 130 of FIG. 10. The transmitter input data signal Iand Q are mixed with the output of the auxiliary VCO 198 of FIG. 15which are then combined and mixed with output of the main VCO 196 ofFIG. 15 using an up converter mixer in the transmitter modulator 206.

The output of the transmitter modulator 206 is preferably fed into ahigh pass filter (HPF) 208 having the data signal below the nominalcarrier frequency of 900 MHz for single side band (SSB) transmission.The output of the high pass filter (BPF) 210 which preferably has acounter frequency of 915 MHz and a band width of 26 MHz. The output ofbandpass filter 219 is fed into two amplifier (AMP) 214 preferablyhaving a gain of 20 and a second amplifier (AMP) 214 preferably having again 30 to provide the necessary transmission output power. The power ofthe data signal at the output of amplifier 214 is nominally at least 1watt which is fed through a lowpass filter (LPF) 216 and a bandpassfilter (BPF) 218. Because of the insertion losses of the filters 216 and218 of 0.7 dB and 3.3 dB respectively, the transmitter 118 has a nominaloutput power of at least 250 mW which is transmitted via antenna 112 ofFIG. 10.

FIG. 17 illustrates the circuitry for selecting between the modes ofmodulation of the present invention. In frequency hopping mode thecorrelator (“CORRELATOR”) 330 us bypassed and the decision and timingrecovery block (“DECISION TIMING RECOVERY”) 332 performs MSK detection.An alternative approach would be to use an FM discriminator, a functionthat is commonly available in limiting amplifier IC's. This is possiblebecause MSK signal are known to be capable of demodulation as either FMor PSK signals.

In DS modes the correlator 330 preferably extracts the data symbols fromthe chipping sequence. The decision and timing recovery block 332outputs send the recovered data (“DATA”) and a clock signal (“CLOCK”) tothe MAC μP 128 for frame processing.

FIG. 18 is a block diagram of the MAC circuitry 128 of FIG. 10. The MACcircuitry 128 is preferably located on the radio interface card 58 ofFIGS. 7, 8 and 9. The medium access control circuitry 128 may beutilized in the protocol of communications media used in a particularcommunications network. The media access circuitry 128 may also utilizethe 2.4 GHz MAC protocols to provide operation on both 9000 MHz and 2.4GHz networks.

The media access protocol may be controlled by a MAC microprocessor(“MAC μP”) 224 which receives a timing control signal from a crystaloscillator (“XTAL”) 246. The MAC microprocessor 224 may communicate withthe electronic device in which the radio of the present invention is tobe utilized via a host communications bus (“HOST”). The MACmicroprocessor 224 may further have input and output signals 248 from ananalog-to-digital converter (“A/D”), digital-to-analog converter(“D/A”), an electrically erasable read only memory (E²ROM”) or a resetcontrol circuit (“RESET”) for example. The MAC microprocessor 224 mayutilize random access memory (“RAM”) 250 which may be either volatile ornonvolatile memory. The MAC microprocessor 244 may also receive an inputfrom OTP 252. A control bus (“CONTROL”) is utilized to control thecircuitry of the radio card 44 of FIGS. 7, 8 and 9.

The MAC microprocessor 244 may have registers to read the status of andcontrol the functions of the radio interface card 58. Registers may alsobe provided to control the transmission power state of the radio of thepresent invention. The MAC microprocessor 244 may provide a parallel-toserial converter for control and programming of the synthesizer 194 ofFIG. 15. Additionally, the MAC microprocessor 224 may provide aprogrammable periodic timer, clock control of the CPU of the dataterminal 10 and PCMCIA programmable clock generation.

FIG. 19 is a block diagram illustrating the host interface circuitry 132of FIG. 10 for radio module 30 of FIG. 7 and for radio/scanner module 20of FIG. 8. The host interface circuitry 132 is preferably located on theradio interface card 58 of FIGS. 7 and 8. A regulator (“REGULATOR”) 254functions as the power supply 134 of FIG. 10 and provides a regulatedvoltage signal to the radio interface card 58 which is connected to theMAC circuitry 128 via a host to MAC communications bus (“TO MAC”) whichconnects to the electronic device in which the radio of the presentinvention is utilized through connectors (“CONNECTORS”) 60 on the radiointerface card 58 of FIGS. 7 and 8. Further connection is made to abuzzer (“BUZZER”) circuit 256 which may be the buzzer 64 of FIGS. 7 and8. A bus connection to the radio/scanner module 20 of FIG. 8 is providedfor control of the scanner 258 which may be a laser scan engine (“LASERSCAN ENGINE”).

FIG. 20 is a block diagram illustrating the host interface circuitry 132of FIG. 10 for PCMCIA radio module 42 of FIG. 9. The PCMCIA radio modulehost interface circuitry 132 is preferably located on the radiointerface card 58 of FIG. 9. A FET switched power supply (“POWER SUPPLYFET SWITCH”) 260 functions as the power supply 134 of FIG. 10 andprovides a supply voltage output (“TO RIC”) to the radio interface card58 of FIG. 9. A microcontroller (“μC”) 262 provides interfacing signals(“TO MAC and PCMCIA CONNECTOR”) between the MAC circuitry 128 of FIG. 2Band the electronic device in which the radio of the present invention isto be utilized through PCMCIA connectors 102 of FIG. 9.

FIG. 21 is a diagram illustrating an alternate configuration of portabledata terminals according to the present invention. Specifically, acommunication network 1450 provides an overall network environment forportable data collection terminals 1454. A host computer 1451 isconnected to access points 1452 via a wired connection 1453. The accesspoints 1452 are in turn communicatively coupled to portable datacollection terminals 1454 via wireless links 1455. The wireless links1455 may be one or more of a plurality of wireless communicationstechnologies, including narrowband radio frequency, spread spectrumradio frequency, infrared, and others.

A dock 1456 and a portable data terminal 1458 according to the presentinvention may be connected to the wired backbone 1453, and may serve afunction similar to an access point 1452. The dock 1456 may providepower to the terminal 1458, or alternatively the dock may be absent andthe terminal 1458 may run for a limited time under the power of itsbattery. The terminal 1458 connects directly to the wired backbone 1453,and also communicates with another terminal 1454 through a wireless link1455. The terminal 1458 may, for example, be equipped with protocolconverter circuitry to convert communication on the wire backbone 1453into wireless communication on the link 1455, and also to convertwireless communication on the link 1455 to a format for communication onthe wire backbone 1453. The communication module associated withterminal 1458 thus improves the versatility of the terminal 1458.

FIG. 22A illustrates one embodiment of the data collection terminal ofthe present invention, having both wired and wireless communicationcapability. A data terminal 1500 is shown having a communication module1502 and a base module 1504. The communication module 1502 contains awired transceiver 1506, a wireless transceiver 1508, and processing andinterface circuitry 1510. The base module 1504 contains a controlprocessor and interface 1512, an application processor 1514, andterminal circuitry 1516 containing data input and display portions andother circuitry well known in the art. The blocks shown in communicationmodule 1502 and base module 1504 are simplified for exemplary purposes,and it will be understood by one skilled in the art that a data terminal1500 according to the present invention is not limited to the blockcircuitry shown in FIG. 22A. In another embodiment, the communicationmodule 1502 may contain additional transceivers for communicating onother mediums and in other networks. The processing and interfacecircuitry 1510 of the communication module 1502 isolates the circuitryof the base module 1504 from the differing operating characteristics ofthe transceivers, so that communication by any of the transceivers canbe accommodated by the circuitry and software routines of the basemodule 1504.

In operation, the processing and interface circuitry 1510 of thecommunication module 1502 is programmed with the network configurationto route communication through either the wired transceiver 1506 or thewireless transceiver 1508. An incoming message on the wired transceiver1506 may be routed and processed to a terminal display portion, or maybe routed to a host computer, a dock, or another portable data terminal1500 through the wired transceiver 1506 or through the wirelesstransceiver 1508, whichever is appropriate. Similarly, an incomingmessage on the wireless transceiver 1508 may be routed to display orthrough the wireless transceiver 1508 or through the wired transceiver1506, whichever is appropriate for the destination. By provided for therouting functions to be done in the communication module 1502, the powerused in the base module 1504 can be minimized. Specifically, theinterface with the control processor 1512 and the application processor1514 need not be used, which allows the main terminal in the base module1504 to remain dormant while communications are routed in thecommunication module 1502.

The choice of which transceiver to use in routing communication is basedon a “least cost” analysis, considering factors such as the powerrequired to send the message through a particular transceiver, the speedat which the message will be received from a particular transceiver, thepossibility of error associated with each transceiver, etc. A wiredconnection is usually selected when available, but routing decisions mayvary with the different characteristics of each message and the mobilityof the terminal. The processing and interface circuitry 1510 in thecommunication module 1502 is preferably capable of performing the leastcost routing analysis for all communication messages without activatingany processing power from the base module 1504.

FIG. 22B is a diagram illustrating a specific implementation of theportable terminal of FIG. 22A a single PCMCIA card contains not only amulti-mode wireless transceiver, but also a wired modem transceiver. Inparticular, a portable terminal 1520 contains terminal circuitry 1522comprising processing circuitry 1526, conventional terminal circuitry1528 and interface circuitry 1530. The interface circuitry 1530 providesa PCMCIA interface for receiving PCMCIA cards of various functionality.The terminal circuitry 1522 is well known and can be found inconventional portable or hand held computing devices.

Via the interface circuitry 1530, the portable terminal 1520 acceptsPCMCIA cards. As illustrated, the PCMCIA card inserted constitutes acommunication module 1524 which provides both wired and wireless access.Specifically, the communication module 1524 comprises processingcircuitry 1532, a multi-mode wireless transceiver 1534 (such as setforth previously), a wired modem transceiver 1536 and interfacecircuitry 1544. When in use, the wired modem transceiver 1536 interfacesvia a jack 1540 to a telephone line (not shown). Similarly, the wirelessmulti-mode transceiver 1534 communicates via an antenna 1538.

Whether the modem transceiver 1536 or multi-mode transceiver 1534 isbeing used, the processing circuitry 1526 always delivers and receivesdata and messages via the interface circuitry 1530 in the same mannerand format, i.e., the interface circuitry 1530 supports a commoncommunication interface and protocol. The processing circuitry 1532 ofthe communication module 1524 receives data and messages via theinterface circuitry 1544. If the modem transceiver 1536 is being used,the processing circuitry 1532 appropriately (de)segments and(de)compresses the data/messages utilizing a digital signal processor(DSP) 1542. Otherwise, the processing circuitry 1532, including the DSP1542, participate to assist in wireless communication via the multi-modetransceiver 1534. Thus, the module 1524 not only saves on PCMCIA slots(as required when a conventional radio card and a conventional modemcard are both being used), but also saves costs and increasesreliability by sharing common circuitry resources. In particular, themodem and multi-mode transceivers 1536 and 1534 share the interfacecircuitry 1544 and processing circuitry 1532 which includes the DSP1542.

FIG. 23 is a diagram illustrating the use of portable terminalsaccording to the present invention utilizing both wired and wirelesscommunication in a network configuration. Specifically, a server 1515 isshown connected to mobile computing devices (MCDs) 1554 via a wiredcommunication link 1552. The communication link 1552 may alternativelybe an infrared link, or another communication technology. MCDs 1554 areconnected to each other and to the server via the link 1552. MCDs 1554are also communicatively coupled to each other via wireless links 1556.

The network involving the server 1550, the communication link 1552, andthe MCDs 1554 represents a primary communication network, that ispreferable to use when there are no interference or disconnectionproblems in the network. The network between MCDs 1554 involvingwireless links 1556 represents an auxiliary or backup network, which isused where there are problems with the primary network, or to rundiagnostics on the primary network. The MCDs 1554 are equipped toautomatically switch from the primary network to the auxiliary networkwhen a problem arises on the primary network. This network redundancyallows the MCDs 1554 to remain in constant communication with each otherand with server 1550.

For example, a wired network on a communication link 1552 does notrecognize connection well, and may not immediately detect a loss ofconnectivity. MCDs 1554 utilize wireless links 1556 to diagnose a lackof connection on the wired network 1552. For example, an MCD 1554 mayactivate its radio to send a test message to another component of thenetwork, either another MCD 1554 or the server 1550, to testcommunication on the wired link 1552 by sending a reply test messageback to the inquiring MCD 1554. The test routine is preferablyimplemented and controlled by the processing/interface circuitry 1510 inthe communication module 1502 (see FIG. 49) of the MCD 1554. If thereply communication test is not received, the MCD 1554 will know thatthere is a problem on the primary network, and will inform other MCDs1554 to switch to the auxiliary network. The MCDs 1554 can continue tocheck the primary network via wireless links 1556 until the primarynetwork is back in service.

Some MCDs 1554 may be out of range to effect wireless communication withserver 1550 by a wireless link 1556. An out-of-range condition isdetermined according to the particular communication and connectionprotocol implemented by MCDs 1554 and other network components such asserver 1550. In this situation, the out-of-range MCD 1554 sends itsmessage, along with an out-of-range condition indicator, to another MCD1554 that is in communication with the server 1550, and the in-range MCD1554 forwards the message on to the server. Similarly, the server 1550sends its messages intended for the out-of-range MCD 1554 to an in-rangeMCD 1554 to be forwarded over a wireless link 1556. The MCDs 1554 arecapable of automatically switching from the wired network to thewireless network and vice versa for each communication attempt.

FIG. 24 is a diagram illustrating the use of portable data terminalsaccording to the present invention utilizing both wired and wirelesscommunication to access separate subnetworks in an overall communicationnetwork. Specifically, a wired network includes wired server 1600 andmobile computing devices (MCDs) 1606 connected by a wired communicationlink 1604. MCDs 1606 are also part of a wireless network with wirelessserver 1602, and are communicatively coupled to each other and thewireless server 1602 via wireless communication links 1608. Wirelesslinks 1608 may be radio frequency communication links, such asnarrowband, direct sequence spread spectrum, frequency hopping spreadspectrum or other radio technologies. Alternatively, wireless links 1608may be infrared communication links, or other wireless technologies. Inanother embodiment, the wired server 1600 and the wired communicationlinks 1604 may utilize infrared communication technology, with thewireless communication links 1608 being radio frequency links. Thepresent invention contemplates various combinations of communicationtechnologies, all accommodated by communication modules of MCDs 1606.The communication modules of MCDs 1606 include any number oftransceivers operable on any number of communication mediums, since thedifferences in their operating characteristics are isolated from thebase module of the MCDs 1606 by a communication processor. The MCDs 1606are preferably able to automatically switch between the wired andwireless networks, controlled primarily by a communication processor intheir communication modules.

Some MCDs 1606 may be out of range to effect wireless communication withwireless server 1602 by a wireless link 1608. An out-of-range conditionis determined according to the particular communication and connectionprotocol implemented by MCDs 1606 and other network components such aswireless server 1602. In this situation, the out-of-range MCD 1606 sendsits message, along with an out-of-range condition indicator, to anotherMCD 1606 that is in communication with the wireless server 1602, eitherover a wireless link 1608 or alternatively over a wired link 1604 ifboth MCDs 1606 are constituents of a wired network. The in-range MCD1606 then forwards the message on to the wireless server 1602 overwireless link 1608. Similarly, the wireless server 1602 sends itsmessages intended for the out-of-range MCD 1606 to an in-range MCD 1606to be forwarded over a wireless link 1608 or a wired link 1604, if bothMCDs are constituents of a wired network.

FIG. 25a is a block diagram illustrating an embodiment of the presentinvention wherein a wireless access device uses a dedicated control/busychannel to manage a plurality of modes of communication with roamingterminals. Specifically, a wireless access device 1701 managescommunication in a cell of network with a plurality of wirelessterminals, such as a wireless terminal 1703. The network may contain aplurality of other cells each managed by an associated wireless accessdevice to provide site or premises wide ubiquitous wireless coverage forthe plurality of stationary and roaming wireless terminals. Asillustrated, for example, the network may also contain wiredcommunication links therein as provided, for example, by a wiredEthernet backbone LAN 1705.

The wireless access device 1701 comprises control circuitry 1711, amultimode transceiver 1713, an Ethernet transceiver 1715 and an antenna1717. The Ethernet transceiver 1715 supports communication between thebackbone LAN 1705 and the control circuitry 1711. Similarly, themultimode transceiver 1713 supports communication into a wirelessnetwork cell to wireless devices within range such as the wirelessterminal 1703 via the antenna 1717. The multimode transceiver 1713 ismore fully described below in reference, for example, to FIG. 1C.

A wireless terminal 1703 also comprises a multimode transceiver, amultimode transceiver 1721, as well as an associated antenna 1723 andconventional terminal circuitry 1725. Using the multimode transceiver1721 and associated antenna 1723, the wireless terminal 1703communicates with the wireless access device 1701 when it is withintransmission/reception range.

The wireless access device 1701 selects (and may periodically reselect)one of a plurality of communication modes and associated parameters ofoperation based on a variety of factors mentioned previously such asrecent success rate, RSSI, neighboring cell operation, etc. However,when the wireless terminal 1703 roams within range of the wirelessaccess device 1701, the roaming terminal must identify the currentlyselected mode and associated parameters being used by the wirelessaccess device 1701 to maintain the cell's communication. Although thewireless terminal 1703 could be configured to scan each available modeto identify the currently selected mode and parameters, such effortsoften prove time consuming.

Instead, the wireless terminal 1703 and wireless access device 1701 arepreconfigured with mode and parameter information that defines adefault, busy/control channel. Thus, upon roaming into range of thewireless access device 1701, the wireless terminal 1703 first switchesto the busy/control channel by operating the multimode transceiver 1721according to the preconfigured mode and parameters, and then beginslistening. Within a predefined maximum time period thereafter, thewireless terminal 1703 will receive transmissions from the wirelessaccess device 1701 identifying the currently selected communicationchannel mode and associated parameters. The wireless access device 1701periodically broadcasts such information on the busy/control channel tocapture terminal that happens to need communication channel definitions(e.g., selected mode and parameters) to participate. The wirelessterminal 1703 utilizes identified mode and associated parameterinformation to switch the multimode transceiver 1721 over to theselected communication channel and begins participation thereon.

FIG. 25b is a drawing illustrating advantageous operation of thewireless access device of FIG. 25a when configured to handle hiddenterminal conditions. In particular, each of wireless terminals 1751 and1753 is configured to only switch from the busy/control channel (havingpredefined mode and associated parameters) to the communication channel(selected by a wireless access device 1755) when there is a need foraccess to the communication channel and the communication channel isclear (available). In this configuration, when no desire to communicateis present, the terminals 1751 and 1753 need only occasionally check thebusy/control channel to identify any outstanding messages orcommunication requests as transmitted by the wireless access device1755. If either terminal 1751 or 1753 desires to participate on thecommunication channel (to initiate communication or to respond toawaiting messages or communication requests), that terminal need onlymonitor the busy/control channel long enough to identify a clearcommunication channel before switching over to the communication channelto participate. As before, the wireless access device 1755 alsoperiodically identifies the communication channel mode and associatedparameters as selected and reselected by the wireless access device1755.

To fully appreciate this process, first assume that the wirelessterminals 1751 and 1753 are not within range of the wireless accessdevice 1755. Upon wandering within range of the wireless access device1755, the wireless terminal 1751 utilizing the predefined mode andparameters begins listening for transmissions on a busy/control channel.Within some time period thereafter, the wireless access device 1755participates on the busy/control channel to transmit: 1) the currentlyselected communication channel definition (i.e., mode and parameters);2) pending message and communication request indicators; and 3) currentchannel conditions. After identifying a need to participate, thewireless terminal 1751 awaits a transmission from wireless access device1755 (on the busy/control channel) that the selected communicationchannel is clear (not in use). When the channel is clear, the wirelessterminal 1751 adopts the selected communication channel definition andbegins participating thereon.

Second, assume that, while the wireless terminal 1751 is engaged inongoing communication with a computing device 1761 on a backbone LAN1763 via the wireless access device 1755, the wireless terminal 1753comes within range of the wireless access device 1755 and desires toparticipate on the currently selected communication channel. Thewireless terminal 1753 adapts itself to participates on the busy/controlchannel and identifies, in periodic transmissions from the wirelessaccess device 1755, that the communication channel is busy. Thus, thewireless terminal 1753 must monitor the busy/control channel to identifywhen the communication channel is clear before adapting to thecommunication channel to participate.

This operation works whether or not the terminals 1751 and 1753 arewithin range of each other. In particular, the terminal 1751, terminal1753 and access device 1755 have transmission ranges illustrated bydashed circles 1771, 1773 and 1755, respectively. Although bothterminals 1751 and 1753 are within range of the access device 1755,neither are in range of each other and, thus, are referred to as“hidden” from each other. The access device 1755 is within range of bothof the terminals 1751 and 1753. If the wireless terminal 1753 attemptedto transmit on the communication channel while the terminal 1751 wastransmitting, a collision would occur at the wireless access device1755. However, this is not the case because both of the terminals 1751and 1753 must receive a communication channel clear indication on thebusy/control channel from the wireless access device 1755 that is inrange of both, avoiding the hidden terminal problem. When participationis completed on the communication channel, the terminals 1751 and 1753readopt the busy/control channel definition (i.e., mode and associatedparameters).

Participation by the wireless access device 1755 on the busy/controlchannel need only be by transmitting, although receiving might also beemployed in case the busy/control channel is to be shared. Similarly,participation by the wireless terminals 1751 and 1753 need only be byreceiving transmissions, although transmitting might also be employed.In particular, transmission might be employed by a wireless terminal onthe busy/control channel if the wireless terminal does not support thecurrently selected communication channel, i.e., does not support themode and associated parameters.

In addition, should the two terminals 1751 and 1753 be within range ofeach other and desire to intercommunicate. the wireless access device1755 will allocate an unused, non-competing mode in which the twoterminals can exchange information or data. In particular, one of thewireless terminals 1751 and 1753 first attempts to establish an exchangeby gaining access to the communication channel (via busy/control channelmonitoring). Once access has been established, the wireless terminal,e.g., the terminal 1751 delivers a request for poll message (RFP) to thewireless access device 1755 which identifies the amount of data orinformation to be exchanged if known, the recipient or target (e.g., theterminal 1753), and characteristics of the data or information such aswhether real time dedicated bandwidth is not needed, desired orrequired. If the amount of data or information to be exchanged isminimal and requires no dedicated bandwidth, the wireless access device1755 will not bother attempting to dedicate a mode to the transceivers1751 and 1753. Instead, the wireless access device 1755 will merelyrelay the information or data received from the terminal 1751 to theterminal 1753 and vice versa. Otherwise, the wireless access device 1755will examine its lookup table to see if the terminal 1753 currentlyparticipates within the network cell (i.e., within range) of thewireless access device 1755. If the terminal 1753 doesn't participate,the wireless access device 1755 will inform the terminal 1751 and onlyproceed with relaying functionality (or spanning tree wireless routing,for example) per confirmation by the terminal 1751. However, if theterminal 1753 does participate, the wireless access device 1755concludes that there is a good chance that the terminals 1751 and 1753are within range of each other. Thus, the wireless access device 1755attempts to identify an available and appropriate mode and associatedparameters that may be temporarily assigned to the terminals 1751 and1753 for their communication exchange. The wireless access device 1755attempts to communicate such channel information to both of theterminals 1751 and 1753. Thereafter, as soon as either of the terminals1751 and 1753 receive the information, the terminal will immediately settheir multimode radio to the dedicated mode and parameters, listen forpolling messages from the other terminal, and, if no poll messages aredetected, begin transmitting polling messages to the other terminal. Ifa polling message is received, the communication exchange, such asdedicated voice bandwidth, will take place. Afterwards, the terminals1751 and 1753 inform the wireless access device 1755 that the allocatedchannel is no longer needed and may be reallocated. Similarly, if aterminal polls for the other for a predefined period of time on theallocated channel without receiving any response, that terminal willinform the wireless access device 1755 of the failure, and the wirelessaccess device will free the allocated mode for reallocation orcommunication channel use.

FIG. 25c is a flow diagram illustrating the functionality of oneembodiment of the wireless access device of FIG. 25b in managing acommunication channel using a second channel, i.e., the busy/controlchannel. The wireless access device maintains ongoing communication orotherwise waits in an idle state at a block 1781. If a predeterminedtime out period (e.g., a B/C service time period) lapses while theaccess device is in an idle state as indicated at a block 1782, theaccess device switches to the predefined mode and associated parametersof the busy/control channel at a block 1783. At a block 1784, on thebusy/control channel, the access device transmits: 1) the currentlyselected communication channel definition (mode and parameters); 2)channel status indications; and 3) pending message/communication requestindications. Thereafter, at a block 1785, the access device switchesback to the selected communication channel mode and parameters, resetsthe B/C service time period (at a block 1786) and returns to the block1781 to participate on the communication channel.

If, while participating on the selected communication channel at theblock 1781, a request for poll (RFP) transmission is received from awireless terminal as indicated at an event block 1787, the wirelessaccess device responds by switching to the busy/control channel at ablock 1788 to deliver communication channel definition, channel “busy”indications and any pending message/communication request indications ata block 1789. Although the busy indication may only indicate that theselected communication channel is not available, it also indicates anestimated amount of time during which the channel will be busy. Thewireless access device derives this estimate from the overall data sizeto be transferred as determined from the data itself or from a field inthe RFP transmission, if known. This way, a waiting wireless transceivermay go to sleep while an ongoing exchange is taking place and wake upwhen the exchange is scheduled to have finished.

Thereafter, at a block 1790, the wireless access device switches back tothe selected communication channel mode and parameters, resets the B/Cservice time period (at a block 1791), transmits a Poll or Data message(whichever is appropriate under the circumstances) on the communicationchannel at a block 1792, and returns to the block 1781 to await a Dataor Ack (acknowledge) message from a participating wireless transceiver.In particular, in response to an RFP from a participating wirelessdevice that has Data to deliver via the wireless access device, thewireless access device delivers a Poll message at the block 1792 to theparticipant, prompting for the Data. Otherwise, if the RFP indicates adesire by the participating wireless terminal to receive Data, thewireless access device sends the Data at the block 1792. The Data sentat the block 1792 may be of any length including dedicated bandwidth foran unknown duration. Thus, if a wireless terminal listens for a periodof time greater than the B/C service time period and detects notransmission from the access device on the busy/control channel, thewireless terminal concludes that the selected communication channel isbusy.

Alternately, data may be segmented into Data packets for transmissionone packet at a time via the blocks 1781 and 1787-92. In this way, alistening wireless terminal will can be sure that it will receive acommunication channel broadcast via the blocks 1782-86 between each Datapacket transmission. Upon receipt, wireless terminals may place theirtransceivers in a sleep mode until each of the Data packets of the datahave been exchanged, and the communication channel is clear.

Upon receiving the data (or Data packet) or an acknowledge (ACK) messageindicating successful receipt of data (or a Data packet) as indicated atan event block 1793, the wireless access device broadcasts a Poll, Ackor Clear message or sends data (or packets thereof) as provesappropriate at a block 1798. The access device then switches to thebusy/channel at a block 1794 to transmit the currently selectedcommunication channel definition, busy or clear indications and pendingmessages/requests at a block 1794. Afterwards, the wireless accessdevice switches back to the communication channel at a block 1796,resets the B/C service time period at a block 1797 and returns to theblock 1781 to continue communication exchanges or enter an idle state ifthe exchange is complete.

FIG. 26a is a block diagram illustrating an alternate embodiment of thatshown in FIG. 25a wherein a wireless access device uses a separatetransmitter for the dedicated control/busy channel and a roamingterminal uses either a shared multimode transmitter or a multimodetransmitter and a separate busy/control channel receiver. In theprevious embodiments of FIGS. 25a-c, the wireless access device andwireless transceivers each used a multimode transceiver to supportparticipation on two wireless channels: the selected communicationchannel and the busy/control channel. As illustrated, this need not bethe case. Instead, a wireless access device 1801 participates using tworadios when communicating with a wireless transceiver 1803 (having onlya single multimode radio) and a wireless transceiver 1805 (having tworadios). With a dual radio configuration, participation on both channelsmay occur at the same time, increasing overall performance in manycircumstances.

In particular, a wireless access device 1801 comprises control circuitry1811, an Ethernet transceiver 1813, a busy/control transmitter 1815 andcorresponding antenna 1817, and a multimode transceiver 1819 andcorresponding antenna 1821. Having separate radio units and antennas,the wireless access device 1801 participates on: 1) a selectedcommunication channel defined by mode and parameter information,servicing data exchanges in the communication network cell; and 2) thebusy/control channel defined by predetermined mode and parameterinformation known to all wireless transmitters, controlling access tothe selected communication channel. Such participation is oftensimultaneous, preventing a wireless terminal from having to wait long onthe busy/control channel for a transmission.

In one configuration, where hidden terminals prove to be of littleconcern, the wireless terminals 1803 and 1805 are only forced to wait onthe busy/control channel until they receive the selected communicationchannel definition. In another configuration. as better exemplified inFIG. 26b which follows, all wireless terminals participate on thebusy/control channel except when they have a need and gain access to theselected communication channel. In this latter configuration, when thewireless access device 1801 is participating on the selectedcommunication channel with the wireless terminal 1805, for example, thewireless access device 1801 concurrently delivers communication channeldefinition, busy/clear status and message/request indications on thebusy/control channel. Such information can be repeatedly transmitted atany time interval desired or may be transmitted continuously.

Similarly, although a wireless transceiver may operate with a singlemultimode radio as described previously, it may also take advantage ofmultiple radios. Specifically, the wireless transceiver 1803 comprisesterminal circuitry 1831 and only one radio, a multimode transceiver1833. Thus, the wireless transceiver 1803 is forced to time shareparticipation on the busy/control channel and the selected communicationchannel—often all that is needed. However, the wireless terminal 1805comprises terminal circuitry 1845 and two radios, a busy/control channelreceiver 1847 and a multimode transceiver 1849. As such, the wirelessterminal 1805 may place the multimode transceiver 1849 in a low powerstate, and only powering up its busy/control channel receiver 1847 tocheck in. Characteristics of the busy/control channel may be chosen topermit significant overall power savings and simplicity in the design ofthe receiver 1847.

FIG. 26b is a drawing illustrating advantageous operation of thewireless access device of FIG. 26a when configured to overcome thehidden terminal conditions. As with FIG. 25b, the range of a wirelessaccess device 1911 is defined by a dashed circle 1913. Similarly, thewireless terminals 1915 and 1919 have ranges defined by dashed circles1917 and 1921, respectively. The wireless terminals 1915 and 1919 areout of range of each other. The wireless access device 1911 is withinrange of each of the wireless terminals 1915 and 1919.

Unlike the wireless access device 1755 (of FIG. 25b), the wirelessaccess device 1911 participates on both a busy/control channel and aselected communication channel simultaneously. The wireless accessdevice 1911 delivers all communication channel information eithercontinuously or periodically on the busy/control channel, while idle orservicing any wireless terminal on the communication channel. By doingso, the wireless access device 1911 is free to set any length datasegments or none at all on a selected communication channel, whiledelivering communication channel information as often as desired on thebusy/control channel. Thus, the busy/control channel and communicationchannel can be designed for optimized performance without having toconsider time sharing of a single channel or time sharing a transceiver.

Thus, the busy/control channel can be designed to minimize the listeningtime of the wireless terminals 1915 and 1919 to gain status information.Sleep periods of the wireless (and often hand-held and portable)terminals 1915 and 1919 increased saving critical battery power.Similarly, data segmentation can be set based solely on the conditionsof the selected communication channel, and not merely to guarantee thewireless access device 1911 a maximum interleaving time period duringwhich the wireless access device 1911 will participate on thebusy/control channel.

FIG. 26c is a flow diagram illustrating the functionality of oneembodiment of the wireless access device of FIG. 26b in managing acommunication channel using a control/busy channel with dual radios.Specifically, a wireless access device waits in an idle state or isengaged in ongoing communication on the selected communication channelat a block 1951. As soon as a B/C time period lapses as indicated by anevent block 1953, the wireless access device branches to a block 1955 totransmit mode, parameter and status information regarding the currentlyselected communication channel along with indicators of pending messagesand communication requests. Afterwards, the wireless access deviceresets the B/C time period at a block 1957 and branches back to theblock 1951 to continue servicing the selected communication channel orreenter an idle state. Thus, a preset (B/C time period) intervals, thewireless access device delivers the selected communication channelinformation on the busy/control channel. The B/C time period may beconfigured to either minimize transmission overhead or minimize wirelessterminal listening times. The B/C time period might also be set to zero,causing the wireless access device to continuously transmit the selectedcontrol channel information (i.e., the selected mode and parameters,busy or clear status, predicted duration of a current exchange, andpending messages and communication requests). The B/C period is thus asynchronous period. Thus, a maximum value of the B/C period (or an othercommonly known value) provides a wireless terminal with a guaranteedmaximum listening time.

Although the B/C time interval may prove sufficient to communicateupdates to the selected communication channel information, the wirelessaccess device is also configured to immediately identify any mode orparameter changes of the selected communication channel. In particular,at a block 1961, if for any of a variety of reasons the wireless accessdevice decides to switch the mode and/or parameters of the communicationchannel, the wireless access device vectors to immediately deliver suchinformation on the busy/control channel via the blocks 1955 and 1957.Similarly, the wireless access device may also be configured (asindicated by the dashed lines) to respond to immediately report statuschanges such as whether a message or a request for dedicated bandwidthhas been received as indicated at a block 1963 and the blocks 1955 and1957. Other immediate event servicing may also be added and similarlyserviced.

Unlike the single radio (shared) embodiments previously mentioned, thewireless access device services the block 1955 and 1957 no matter whatthe wireless access device is currently engaged in on the selectedcommunication channel.

FIG. 27 is a block diagram illustrating further embodiments of thepresent invention wherein channel selection and operating parameters aredelivered by a wireless access device on a dedicated busy/controlchannel with or without multimode transceiver capabilities. Inparticular, supporting a plurality of wireless terminals such as aterminal 2013, a wireless access device 2011 maintains two channels: acommunication channel and a busy/control channel as previouslydescribed. To carry out such functionality, the wireless access device2011 may comprise control circuitry 2021, an Ethernet transceiver 2023and either a single, configurable transceiver 2025 (for operating onboth the communication and busy/control channels) or a singletransceiver 2025 (for the communication channel which may have onlylimited if any configuration capability) and a single transmitter 2027(for operating on the control channel).

With the single, configurable transceiver 2025, the wireless accessdevice may operate identically to that described in reference to FIGS.25A-C. However, the configurable transceiver 2025 may not providemultimode operation, but only support multiple channels operating in asingle mode. For example, the transceiver 2025 may only support the modeof channelized direct sequence. Although only a single mode isavailable, the parameters such as (and defining) spreading codes,spreading code lengths, channel center frequency and channel bandwidth,for example, alone, and without mode change, provide the wireless accessdevice 2011 with the ability to support a dedicated busy/control channeland provide a plurality of other channels for maintaining thecommunication channel.

Alternatively, the wireless access device 2011 may also comprise adedicated busy/control transmitter 2027. If it does, the wireless accessdevice 2011 with a multimode transceiver 2025 would operate as detailedin reference to FIGS. 26A-C. If configured with a single modetransceiver 2025 supporting only one channel, the wireless access device2011 would still maintain the communication and busy/control channelsbuy need only identify parameter and pending messages and communicationrequests on the busy/control channel. Of course the busy/control channelwould still solve the hidden terminal problems and provide theassociated benefits described above. Finally, with the transmitter 2027supporting the busy/control channel, the transceiver 2025 might supportmultiple communication channels without supporting multiple modes ofoperation. In such configurations, the wireless access device 2011 neednot report mode change information on the busy/control channel.Reporting all other information and aforementioned control would stilltake place.

The wireless transmitter 2013 could accommodate the same wirelessconfiguration as described in reference to the wireless access device2011. Along with conventional terminal circuitry 2029, it may have amultimode or non-multimode, configurable or non-configurable transceiver2031. The transceiver 2031 might operate independently or utilize asupporting busy/control receiver 2033. Lastly, although not necessary,the transmitter 2027 and receiver 2033 might each constitutetransceivers.

As is evident from the description that is provided above, theimplementation of the present invention can vary greatly depending uponthe desired goal of the user. However, the scope of the presentinvention is intended to cover all variations and substitutions whichare and which may become apparent from the illustrative embodiment ofthe present invention that is provided above, and the scope of theinvention should be extended to the claimed invention and itsequivalents. It is to be understood that many variations andmodifications may be effected without departing from the scope of thepresent disclosure.

I claim:
 1. A communication network for collecting and communicatingdata comprising: a wireless access device comprising a control circuitand a first RF transceiver that selectively operates in one of aplurality of different spread spectrum modulation modes; at least onemobile terminal comprising a second RF transceiver that operates in atleast one of a plurality of different spread spectrum modulation modes;and the control circuit being responsive to transmissions received fromthe first RF transceiver for evaluating communication performance anddynamically selecting one of the plurality of spread spectrum modulationmodes of the first RF transceiver while taking into consideration the atleast one of the plurality of spread spectrum modulation modes of thesecond RF transceiver.
 2. The communication network of claim 1 whereinthe plurality of different spread spectrum modulation modes of the firstRF transceiver comprise a direct sequence transmission mode and afrequency hopping mode.
 3. The communication network of claim 1 whereinthe plurality of different spread spectrum modulation modes of the firstRF transceiver comprise a direct sequence transmission mode and achannelized direct sequence mode.
 4. The communication network of claim1 wherein the plurality of different spread spectrum modulation modes ofthe first RF transceiver comprise a frequency hopping mode and a hybridfrequency hopping mode.
 5. The communication network of claim 1 whereinsaid first RF transceiver operates to support a communication channeland a second channel on a time shared basis.
 6. In a communicationnetwork, a plurality of wireless access devices capable of communicatingwith a plurality of wireless terminals, each of the plurality ofwireless access devices comprising: a first radio controllable tosupport a communication channel operating pursuant to one of a pluralityof modes; a second radio supporting a second channel independent of thecommunication channel; a controller that selects one of the plurality ofmodes and controls the first radio to support the selection; and thecontroller utilizes the second radio to communicate on the secondchannel to manage the communication channel.
 7. The communicationnetwork of claim 6, wherein the plurality of modes includes a pluralityof spread spectrum modes.
 8. The communication network of claim 7,wherein the first radio comprises a multimode transceiver and the secondradio comprises a transmitter.
 9. In a communication network, aplurality of wireless access devices capable of communicating with aplurality of wireless terminals, each of the plurality of wirelessaccess devices comprising: a transceiver controllable to operatepursuant to any of a plurality of communication modes; a controller thatselects a communication channel and an independent second channel, thesecond channel transmitting the communication mode in use on thecommunication channel to at least one of the wireless terminals, thecontroller controlling the transceiver to support data routing on thecommunication channel while managing access to the communication channelvia the second channel.
 10. The communication network of claim 9,wherein the plurality of communication modes includes a plurality ofspread spectrum modes.
 11. In a communication network, a plurality ofwireless access devices capable of communicating with a plurality ofwireless terminals, each of the plurality of wireless access devicescomprising: a first radio controllable to support a first communicationchannel operating pursuant to a first mode of a plurality of modes; asecond radio controllable to support a second communication channeloperating independently of the first radio pursuant to a second mode ofthe plurality of modes; and a controller operable to switch from thesecond communication channel to the first communication channel when theneed for access to the communication channel arises.
 12. Thecommunication network of claim 11, wherein the first mode of theplurality of modes includes one of a plurality of spread spectrum modes.13. The communication network of claim 11, wherein the first mode is aspread spectrum communication mode and the second mode is a control modefor managing communication with the plurality of wireless terminals. 14.The communication network of claim 13, wherein the first radio comprisesa multimode radio and the second radio comprises a transmitter.
 15. Thecommunication network of claim 11, wherein the first mode of theplurality of modes includes a communication mode operating in one ormore frequency bands.
 16. A communication network for collecting andcommunicating data, comprising: a wireless access device comprising acontrol circuit and a first RF transceiver that selectively operates inone of a plurality of spread spectrum modes, the plurality of spreadspectrum modes of the first RF transceiver comprising a direct sequencetransmission mode and a frequency hopping mode; at least one mobileterminal comprising a second RF transceiver that operates in at leastone of a plurality of spread spectrum modes; and the control circuitbeing responsive to transmissions received from the first RF transceiverfor evaluating communication performance and dynamically selecting oneof the plurality of spread spectrum modes of the first RF transceiverwhile taking into consideration the at least one of the plurality ofspread spectrum modes of the second RF transceiver.
 17. A communicationnetwork for collecting and communicating data, comprising: a wirelessaccess device comprising a control circuit and a first RF transceiverthat selectively operates in one of a plurality of spread spectrummodes, the plurality of spread spectrum modes of the first RFtransceiver comprising a direct sequence transmission mode and achannelized direct sequence mode; at least one mobile terminalcomprising a second RF transceiver that operates in at least one of aplurality of spread spectrum modes; and the control circuit beingresponsive to transmissions received from the first RF transceiver forevaluating communication performance and dynamically selecting one ofthe plurality of spread spectrum modes of the first RF transceiver whiletaking into consideration the at least one of the plurality of spreadspectrum modes of the second RF transceiver.
 18. A communication networkfor collecting and communicating data, comprising: a wireless accessdevice comprising a control circuit and a first RF transceiver thatselectively operates in one of a plurality of spread spectrum modes, theplurality of spread spectrum modes of the first RF transceivercomprising a frequency hopping mode and a hybrid frequency hopping mode;at least one mobile terminal comprising a second RF transceiver thatoperates in at least one of a plurality of spread spectrum modes; andthe control circuit being responsive to transmissions received from thefirst RF transceiver for evaluating communication performance anddynamically selecting one of the plurality of spread spectrum modes ofthe first RF transceiver while taking into consideration the at leastone of the plurality of spread spectrum modes of the second RFtransceiver.